A lot of for-profit companies have referral programs (which is what this amounts to), and many of them have a similar multilevel marketing component. So this isn't really anything new or novel.
What I would love to see is an social-media site that is willing to take the concept of sharing profits with its members to the next level and organize itself as a cooperative.
Co-ops, unlike for-profit companies, are entirely owned by their members, and thus any profits they make eventually go back to their members, either in the form of greater investment in the site (which benefits the members) or in the form of rebates (where the profits get divided up and distributed to the member-owners, similar to dividends in the for-profit world).
Of course, the problem with organizing as a co-op is that it's harder to come up with capital, because you can't accept outside investment. But with Kickstarter and Indiegogo and the era of fundraiser-driven product development, I don't think that's as much an issue nowadays.
An added bonus of a social network organized as a co-op is that each member-owner gets a vote -- a genuine say in how things are done -- which is often absent in for-profit companies.