User-generated content requires some kind of collaborative moderation. The example below discusses the system pioneered by Slashdot, which is also used by other sites such as Nolog.org about which this citation is taken:
"NoLogo.org is perhaps the most prominent second-generation slash site. This makes it a good example of how the OSI experience, embodied by a specific code, is now at a stage where it can be replicated across different contexts with relative ease. NoLogo.org is based on the current, stable release of Slashcode, an open source software platform released under the GPL, and developed for and by the Slashdot community. Slashdot is the most well-known and obvious example of OSI, since it is one of the main news and discussion sites for the open source movement (www.slashdot.org).
Of particular importance for OSI is the collaborative moderation process supported by the code. Users who contribute good stories or comments on stories are rewarded with "karma," which is essentially a point system that enables people to build up their reputation. Once a user has accumulated a certain number of points, she can assume more responsibilities, and is even trusted to moderate other people's comments. Karma points have a half-life of about 72 hours. If a user stops contributing, their privileges expire. Each comment can be assigned points by several different moderators, and the final grade (from -1 to +5) is an average of all the moderators' judgments. A good contribution is one that receives high grades from multiple moderators. This creates a kind of double peer-review process. The first is the content of the discussion itself where people respond to one another, and the second is the unique ranking of each contribution. This approach to moderation addresses several problems that bedevil e-mail lists very elegantly. First, the moderation process is collaborative. No individual moderator can impose his or her preferences. Second, moderation means ranking, rather than deleting. Even comments ranked -1 can still be read. Third, users set their preferences individually, rather than allowing a moderator to set them for everyone. Some might enjoy the strange worlds of -1 comments, whereas others might only want to read the select few that garnered +5 rankings. Finally, involvement is reputation - (i.e. karma -) based and flexible. Since moderation is collaborative, it's possible to give out moderation privileges automatically. Moderators have very limited control over the system. As an additional layer of feedback, moderators who have accumulated even more points through consistently good work can "meta-moderate," or rank the other moderators." (http://news.openflows.org/article.pl?sid=02/04/23/1518208 )