As to the Facebook comment by BillyS I think you are dead wrong.
I could be wrong, it happened once before…
The problem with social media is loyalty, there is none. What made facebook special was the fact it started as an exclusive club. It was cool because you had to be a student to join. Parental units were explicitly excluded.
Now all I hear are 40 and 50 somethings talking about their facebook accounts. Friending people, it's like reliving your college experience except this time around you stand a chance of being popular...
How uncool is that if you're a student? Mom and dad snooping around your account.
I know all my nieces and nephews (college age) are already looking for something new. And once the younger crowd leaves, all the folks going through a mid life crisis will leave too.
It will be interesting to revisit this thread in three year.