Traditional incentive structure theory is expanded by recent and expansive events such as the Free Software movements and Wikipedia. Massive participation and effort given towards common goals for what would be traditionally understood as no incentive, or even a negative incentive.
Theories espoused by Doc Searls (community gifting) and Yochai Benkler (Commons Based Peer-Production) model these interactions. These theories along with their applications in a wide array of examples from Web2.0 communities suggest specific incentive structures applicable for a Network for shared educational examples.
You can reward site participation with emblems of personal and social value. In many web 2.0 profile sites, it is the norm to provide a user with a 'progress meter' for completion of their profile. These 'progress meters' further incite participation by directing a user to do acts such as 'add a profile image to complete another 10%'.