Only if there's competition. The network effect ensures that there is no competition. Leaving us where we currently are.

Not even, users can just 'not play' (or play less) if the game's no fun.

There are many users for which it is not fun, but an addiction. I have spoken to lots of people who say about once a month something like "Yeah, facebook is really bad for me, I just waste time and get upset", but they can't stop checking it every hour, and responding to posts that touch them emotionally, in either a good or bad way.

That's by design, of course - it benefits Facebook greatly that its herd is addicted, and unlike people addicted to alcohol, nicotine or other substances - there's not even another supplier they can turn to: It's either feed your addiction or suffer withdrawal symptoms.

And I think the success rate of quitters (as a percentage of those who actually want to quit) is also comparable, at single digit percent.