On the future Web 3.0, web spaces will become primarily viewer-oriented. In contrast to the Web-2.0 accounts, Web-3.0 spaces (or graphs) are going to be a collection of web resources from various web sites that are organized essentially based on the view of web viewers. Web-3.0 spaces will become viewer-side home-spaces in contract to the publisher-side home-pages on Web 1.0."
- Yihong Ding 
“I choose to see Personal Web-Server Technology (Opera Unite, Firefox POW, etc) as a breakthrough technology, so people can put their own data into the cloud without paying Flickr or whomever. It is this sort of 'personal technology' I believe will characterize (what we now call) Web 3.0 (and not 3D, or semantic web, etc.). So my dilemma is that, while these technologies are pretty evident today, it is not clear that the people I suspect Pew counts as “the savviest innovators” are looking at them. So I pick “out of the blue” even though (I think) I can see them coming from a mile away.”
– Stephen Downes, National Research Council, Canada 
There are various interpretations as to what is next after Web 2.0:
- Nancy Spivak and Marc Fawzi  believe it will be centered around Semantic Web developments.
- Danah Boyd sees it as centered around place-bound contextualization.
- The Read/Write blog believes that Web 3.0 stands for the opening up of website information to external usage, through Web Scraping and Open API 's
- Nova Spivack sees it as the Web evolving into the real-time Stream 
- Ben Ramsey sees it as connected to Cloud Computing 
My own take (Michel Bauwens) is to see it towards more truly distributed architectures.
Three Phases of Web development
Web 2.0. -- According to the Wikipedia, Web 2.0 is defined as: "Web 2.0, a phrase coined by O'Reilly Media in 2004, refers to a supposed second generation of Internet-based services - such as social networking sites, Wikis, communication tools, and folksonomies - that emphasize online collaboration and sharing among users." I would also add to this definition another trend which has been a major factor in Web 2.0 - namely, the emergence of the mobile Internet and mobile devices (including camera phones) as a major new platform driving the adoption and growth of the Web, particularly outside of the United States.
Web 3.0. -- Using the same pattern as the above Wikipedia definition, Web 3.0 could be defined as: "Web 3.0, a phrase coined by John Markoff of the New York Times in 2006, refers to a supposed third generation of Internet-based services that collectively comprise what might be called "the intelligent Web" -- such as those using semantic web, microformats, natural language search, data-mining, machine learning, recommendation agents, and artificial intelligence technologies - which emphasize machine-facilitated understanding of information in order to provide a more productive and intuitive user experience." (http://communities-dominate.blogs.com/brands/2007/02/evolution_is_un.html)
Expanded Definition of Web 3.0
"Web 3.0 Expanded Definition. I propose expanding the above definition of Web 3.0 to be a bit more inclusive. There are actually several major technology trends that are about to reach a new level of maturity at the same time. The simultaneous maturity of these trends is mutually reinforcing, and collectively they will drive the third-generation Web. From this broader perspective, Web 3.0 might be defined as a third-generation of the Web enabled by the convergence of several key emerging technology trends:
§ Broadband adoption
§ Mobile Internet access
§ Mobile devices
§ Software-as-a-service business models
§ Web services interoperability
§ Distributed computing (P2P, grid computing, hosted "cloud computing" server farms such as Amazon S3)
§ Open API 's and protocols
§ Open data formats
§ Open-source software platforms
§ Open data (Creative Commons, Open Data License, etc.)
§ Open identity (OpenID)
§ Open reputation
§ Portable identity and personal data (for example, the ability to port your user account and search history from one service to another)
The Intelligent Web
§ Semantic Web technologies (RDF, OWL, SWRL, SPARQL, Semantic application platforms, and statement-based datastores such as triplestores, tuplestores and associative databases)
§ Distributed databases -- or what I call "The World Wide Database" (wide-area distributed database interoperability enabled by Semantic Web technologies)
§ Intelligent applications (natural language processing, machine learning, machine reasoning, autonomous agents) (http://communities-dominate.blogs.com/brands/2007/02/evolution_is_un.html)
Web 3.0 is about place and geography:
"In early networked publics, there were two primary organizing principles for group sociability: interests and activities. People came together on rec.motorcylcles because they shared an interest in motorcycles. People also came together in work groups to discuss activities. Usenet, mailing lists, chatrooms, etc. were organized around these principles. By and large, these were strangers meeting. Early net adopters were often engaging with people like them who were not geographically proximate. Then the boom hit and everyone got online, often to email with their friends (and consume). With everyone online, the organizing principles of sociality shifted. As blogging began to take hold, people started arranging themselves around pre-existing friend groups. In this way, the organizing principle was about ego-centric networks. People's "communities" began being defined by their friends. This model is quite different than group-driven structures where there are defined network boundaries. Ego-centric system are a (mostly) continuous graph. There are certainly clusters, but rarely bounded groups. This is precisely how we get the notion of "6 degrees of separation." While blogging (and to a lesser degree homepages) were key to this shift, it was really social network sites that took the ball to the endzone. They made the networks visible, allowing people to put themselves at the center of their world. We finally have a world wide WEB of people, not just documents. When i think about what's next, i don't think it's going more virtual, more removed from everyday life. Actually, i think it's even more connected to everyday life. We moved from ideas to people. What's next? Place. I believe that geographic-dependent context will be the next key shift. GPS, mesh networks, articulated presence, etc. People want to go mobile and they want to use technology to help them engage in the mobile world." (http://www.zephoria.org/thoughts/archives/2007/03/16/web_123.html)
"Turning from the publisher-oriented web to the Viewer-oriented Web is a fascinating transformation. Based on the view of web evolution, the core of this transformation is the upgrade of web spaces.
- On Web 1.0, web spaces were homepages. Homepages typically represented the publishers' view. So Web 1.0 was a publisher-oriented web.
- On Web 2.0, web spaces become individual accounts. Web 2.0 is in a transition from the publisher-oriented web to the viewer-oriented web. Individual accounts are representative units of this transition. Within an account, web viewers collect resources of interest and store them into the account. So these accounts contain significant viewer-oriented aspects. On the other hand, these accounts are isolated in varied web sites, which are typical information organizations built upon the publisher-oriented view. Therefore, individual accounts on these particular sites must inevitably also contain significant publisher-oriented aspects. Such a mixture between the two views causes more problems than benefits. Users feel difficult to organize information across the boundary of web sites.
- On the future Web 3.0, web spaces will become primarily viewer-oriented. In contrast to the Web-2.0 accounts, Web-3.0 spaces (or graphs) are going to be a collection of web resources from various web sites that are organized essentially based on the view of web viewers. Web-3.0 spaces will become viewer-side home-spaces in contract to the publisher-side home-pages on Web 1.0."
Ben Ramsey on Web 3.0 as Cloud Computing
"Web 3.0 represents the next decade of the Web (2010-2019). It will be characterized by a read-write-execute Web, and we will see a proliferation of SaaS and Software + Services models. Software that lives primarily on the desktop will become less and less important as the desktop serves primarily as a client to reach services in the Cloud. I think that we will see rich clients proliferate on the desktop, but, in the end, they will really be using the Cloud for storage/retrieval, and the creation and use of rich clients lends itself well to a REST architecture as rich clients are used to maintain all application state and the messages sent back and forth contain no state at all and are cacheable at every layer of the network… but I digress.
As more and more people become accustomed to storing their data in the Cloud and sharing it with others, our cultural concepts of ownership and privacy will dramatically shift. There could be a widespread backlash as this begins to affect the mainstream culture, or perhaps the backlash will not occur at all as Gen-Xers and Gen-Yers have already begun introducing their parents and grandparents to Web technologies, and they’ve embraced them as a way to keep in touch with their friends and family. I suspect that, by 2015, we’ll have a clear idea of how this shift will play out." (http://benramsey.com/archives/web-10-20-and-30-defined/)
Medicine and Web 3.0
Dean Giustini, UBC biomedical branch librarian:
"In medicine, finding the best evidence has become increasingly difficult, even for librarians. Despite its constant accessibility, Google’s search results are emblematic of an approaching crisis with information overload, and this is duplicated by Yahoo and other search engines. Consequently, medical librarians are leading doctors back to trusted sources, such as PubMed, Clinical Evidence, and the Cochrane Library, and even taking them to their library bookshelves instead. Unless better channels of information are created in web 3.0, we can expect the information glut to continue.
Web 3.0 is likely to have a big effect on medicine in 2008. In bioinformatics, it will become more common to process ever larger amounts of data. In fact, experts in bioinformatics already search for data from disparate systems, and they have started to build rich semantic relations into information tools for knowledge discovery. Finally, greater capacity for creating knowledge in medicine will be possible if we have the will to publish clinical data openly and transparently, and subject it to scrutiny.7
Developing a more personalised healthcare system will be an important challenge for doctors in web 3.0. In an era of greater personalisation, treating patients’ health problems according to their genetic profiles will depend on using the latest information technologies.8 Even the treatment of new diseases and warning systems for natural disasters will benefit from the merging of epidemiological datasets with virtual, three dimensional tools like Google Earth. Making the search for health information efficient and responsive to patients’ needs will also help reduce the costs of medical treatment.
Social software enthusiasts may well find that the new web will be fertile ground for the creation of knowledge. Although already popular, wikis may well serve as platforms for the exploration of web 3.0. One innovative wiki—Wikiproteins—is already using semantic technologies. In contrast to other wikis, Wikiproteins imports data mined from several of the world’s leading biomedical databases, such as PubMed, UniProt, and the National Library of Medicine. Its integrated entries are a useful combination of genetic information and scientific literature. Notably, the confluence of databases in Wikiproteins yields more than two million factual associations for data mining and over five billion associated pairs.
Each new version of the web should be a better iteration of its predecessor, and web 3.0 should be no exception. In medicine, we should focus on the ability to locate trusted clinical information, while creating the means to produce new knowledge. Information retrieval in web 3.0 should be based less on keywords than on intelligent ontological frameworks, such as the National Library of Medicine’s Unified Medical Language System, Medline’s trusted MeSH vocabulary, or some other tool. The National Library of Medicine is working on automated indexing, which may be part of the solution for searching the biomedical web. Finally, as we move further into the digital age, our trusted print libraries must continue to be well funded and should not be forgotten in the midst of the intelligent web.
The question of whether http://del.icio.us and www.connotea.org—two popular social tagging sites—will be useful in web 3.0 remains doubtful. Social tagging or "indexing" has limitations because of poor control of synonyms, homonyms, spelling conventions, and other linguistic variations. Think about the myriad ways we describe a heart attack; these variations have enormous implications for searching and require control to optimise retrieval. A smarter medical web is coming. Its two most exciting features will be the better organisation of documents and a deeper use of the knowledge base in medicine. In terms of searching, the semantic web should resemble a library catalogue, where documents are described and given meaningful access points for easy retrieval. However, in getting to web 3.0, let’s aim for something better than the current web, not the incoherent mess of web 2.0. Logically, web 3.0 should bring order to the 21st century web in the same way that Dr John Shaw Billings’s Index Medicus brought order to medical research back in the 19th century. As a medical librarian, I sincerely hope that web 3.0 will return us to some of the time honoured principles of my profession." (http://www.bmj.com/cgi/content/full/335/7633/1273?ijkey=9SxFZeml2Rt3Jza&keytyperef)