One thing we learned, as a general rule, it is difficult to effectively pay people to create good content on a social network.
The best and most knowledgeable people want to create content based on intrinsic motivations rather than financial ones.
One only need look at Wikipedia, Stackoverflow, Quora, etc to see intrinsic motivation inspiring good content.
I guess the main point is that once you start paying people then the intrinsically motivated people aren't as likely to post on the same place.