In short, see 80/20 rule. Once you've hit 80 you probably should look at growing horizontally.

I don't use Facebook but I'm under the impression they've done this somewhat with local market places, games & video streaming.

It sounds to me that you're sick of common abused marketing tactics or maybe it's just that I am & therefore that's how I read your post. Gamification, Deadly Sins, Reciprocity, etc..