They really have a leg up to introduce earning based currency into their site as well as use it as an opportunity to clean up the junk that circulates there. If they went with just pure monetary gains then rewarding FB users with tokens based on community interaction and usage would be SO easy for them. That would sink the claws in deeper. If they wanted to take a two step approach they could tie that accumulation of tokens to the quality of user's posts and introduce things like downvoting. Now that I think about it though, the FB community wouldn't do well with that because if someone posted an opinion contrary to yours then they would just aimlessly downvote instead of having an intelligent conversation about it lol. NM Facebook is a lost cause.

I think draws to communities like this and reddit is the quality of interaction you get with people. Reputation and quality based communities I think are going to have more appeal over the coming years as people get tired of the garbage they have to scroll through on FB.