Social networking sites have a knack for exploding in popularity and then quietly fizzling into oblivion, allowing another to enjoy the momentary spotlight. If a site isn't run into the ground, often times it is purchased by a competing brand. Facebook has yet to face this, having held its own in the social arena since 2004.

The company announced that it now has over 300 million members worldwide -- and it's "just getting started," according to CEO Mark Zuckerberg's blog post yesterday. He added that the social behemoth faces many "fun and important challenges that require rethinking the current systems for enabling information flow across the web."

Zuckerberg also announced that as of last quarter, Facebook is cash flow positive -- something that was not projected to occur until next year. It wasn't long ago that we posted about Facebook hitting the 250 million-member mark -- how large will it be in the years to come?