As part of the CommunityLab project, for the past five years I've been doing research related to incentives for participation in online communities. Now one of my colleagues, Yan Chen, is working with a startup company, urTurn, that has created a cross-platform rewards program. That is, you accumulate points for posting photos or making friend links in social network sites like Facebook and MySpace. Then you turn in the points for prizes.
I'm not quite sure what their business model will be (what do they get from having people accumulate points on their site)? But it will be interesting to see how motivating the points are for people, and how they will prevent various attempts to game the system.
So, sign up, help Yan with her research (she has no financial stake in the company), and win valuable prizes!