Communities of customers organized around brands, products, services, etc...
Summary of original Harvard Business Review article at http://harvardbusinessonline.hbsp.harvard.edu/hbrsa/en/issue/0611/article/F0611E.jhtml?
"Rene Algesheimer and Paul M. Dholakia conducted a yearlong field experiment in collaboration with eBay Germany . 140,120 eBay customers were involved: all active eBay users who had bought or sold on the site within the past three months but had not participated in eBay’s online communities before. From that group, 79,242 randomly selected customers were invited via e-mail to participate in eBay’s customer communities at the beginning of May 2005. They were offered prize incentives such as iPods—worth about €3,000 in total—for doing so. The other 60,878 customers, who were not invited to join the communities, served as the control group.
Within three months, 3,299 of the invitees became active community participants, posting messages, joining in discussions, and helping other members: “community enthusiasts.” An additional 11,242 users became “lurkers,” reading others’ posts without actively participating in the communities themselves.
Over the course of a year, the resaechers compared the behavior of community enthusiasts and lurkers with that of the control group. The differences were astonishing. Lurkers and community enthusiasts
1. bid twice as often as members of the control group,
2. won up to 25% more auctions,
3. paid final prices that were as much as 24% higher
4. spent up to 54% more money (in total).
5. Enthusiasts listed up to four times as many items on eBay
6. Enthusiasts earned up to six times as much in monthly sales revenues as the control users.
The findings on first-time sellers were even more impressive. (....) The increased buying and selling activity of enthusiasts and lurkers generated approximately 56% more in sales during the year of the experiment compared with the previous one. These results show that customer communities pay off handsomely for eBay and the researchers suggest that any online company will benefit from nurturing its communities." (http://i-wisdom.typepad.com/iwisdom/2006/11/customer_commun.html)