Facebook has been able to hook users by the "like" system, which is very addictive. Now, "abusing" something like that may be morally questionable, but my thinking is that a popup notification for every upvote is something I'd like to see. The point behind this is that it would give users a "reward" every time they get upvoted, even if the upvote in question is "super valuable" money-wise.

Also, I made a post about adding "view counts" to posts. It'd be useful for us to know how many people read our posts, even if they don't upvote.

There would be two effects: it would guide us to make content thatb more people like, and it would give us something to "follow". People play online games because we have this "innate" need to grow, develop and evolve. Seeing our view counts go up would be hooking.