I think social sharing is a good first start- people like the stuff their friends like. For example, I might read your facebook feed (if I didn't hate facebook) because I know you, but I'm not going to go read some randos facebook feed. That would just be boring. and weird.
My point is, social only gets you so far. You share with your friends, your friends share with you- but then it actually does break down. If you look at preceieved sense of authority, trust drops almost 2 fold when its a "friend of a friend- instead of a friend. You run the risk of having all of these "cells of authority" that don't interact.
But the good news is, traditional forms of authority can solve this problem. People seek out and read content all of the time that isn't recommended by their friends. They read it because they think its a good source of information. And because they think the person who is writing it is an authority (or at least entertaining).
I think you want to make sure that your platform encourages this kind of authrity as well. You want people to have shared web channels that people read like they read tech crunch or the wall street journal. This is important because 90% of all content consumers (and in my opinion, its really more like 99%) are passive. All they do is read. They don't create. They don't share.
But the do click your ads. So its smart to think about how this product is for them.