Revenue Sharing
If content is created 'at the edges' by multiple authors, and if the participatory platforms are living of the content created by all, it makes sense to develop revenue sharing shemes that benefit the individuals, communities and corporate organizers of the platform.
Such schemes are monitored by Pete Cashmore at http://mashable.com/category/revenue-sharing/
Examples of some 'peer reward' schemes implemented by legal musical filesharing systems:
Peer Cash, http://www.peerimpact.com/peercash.html
Peer Reward, http://www.gridnetworks.com/?section=solutions-ol-rewards