(First: Sorry for the post dearth - its August, what can I say?)
It started a bit slowly, but since Facebook opened up its doors to all comers, its become quite the deluge from my social circles (way behind on friend approvals still) - it took LinkedIn many years to achieve any critical mass for me.
Zero to hero very quickly... obviously curiosity and, quite frankly, a well thought out product with a positive developer eco-system have been rewarded (remember this idea?). In fact, no coincidence, I think, that developer APIs coincide with Facebook's recent rapid rise beyond the college crowd... this is how you go from narrow to general: by letting your application become a platform.
That is, you succeed best by letting others success feed you.
So, I'd been meaning to blog about this upswing for a few weeks now... and then I ran into this today:
Ick, old married guys on Facebook
It speaks for itself: Perspective is everything :)