How Many Will Be Left

There are tons of social networking sites popping up all over the place and for just about anything you can think of. Many of them won't survive. That's just the nature of things. Most businesses don't survive a year, most Web hosting sites don't last 5 years.
Is their time running out? How long do you think most of these smaller social networking sites will last? One year, three, five? How many do you think will be left 2 years from now, or even one?
~admin