I am observing the opposite: the mainstream public (looking at my non-techie friends) have been fully exposured to it, had enough of it, and is slowly getting tired of it. We're not talking about early adopters anymore: everybody has an online identity and has learned its limitations and implications.
If anything, social networks are getting boring: outside of your real circle of friends you see the same strangers posing to be smarter, better looking and happier than they really are: people aren't that different after all, and your real social network stays where it has always been: in your cell phone's address book.
And that's where I'll be turning to for an advice about finding a doctor or a car mechanic. I don't give a rat's ass about what "people on the internet" have to say. At least half of them voted for Bush. Twice.