Slowly and painfully due to apathy most likely.
The other option is some revolutionary, yet popular (unlike G+ launch), alternative.
As someone who is just 24 and graduated in May '11, I found my Facebook use plummet after graduation. Same for my friends. We have less time to kill stalking each other, I suppose. I don't really even post any updates and the same can be said for many of my friends who could have been former FB addicts in college.
I would fully dump it if it weren't still a popular option to coordinate events among people - especially if visiting friends in another city or similar.