TPTB, using a social network doesn't equate to "working". You are miscorrelating the two. You are correct in the fact that people share for much more valuable reason than ad revenue. That fact leads me to ask, "Wouldn't you rather use a social network which rewarded you for your participation instead of a centralized entity?"
I am not "miscorrelating" any thing here. Earning miniscule revenue for sharing isn't a compelling feature.
I haven't seen any compelling feature or niche articulated for Synereo. I've read a 50+ page Synereo white paper of technobabble about process calculi.