Justin Bieber Hits Twitter Milestone

Justin Bieber's broken the 6-million follower mark on Twitter.

Bieber thanked his fans for helping him get there, tweeting, "6 MILLION OF THE GREATEST FANS ON EARTH ON TWITTER!!!! THANK U. 

This is crazy... My Hometown only has 30,000 people total! NUTS."

Given the popularity of social networking sites, do you think they're just a passing fad or are they here to stay?