In it's latest market report, British communications watchdog, Ofcom cited a 5 percent decline in the number of 15-24 year olds using social networking sites such as Facebook. Although overall usage was up for all other age groups, social media sites, marketers, and advertisers have an especially keen interest in the 15-24's due to this group's tendency to lead the social media trends.

Ofcom also reported a steep climb in Twitter's popularity. Usage has increase from .1 million Tweeters over the past year to 2.6 million in May of 2009.

That being said, where are these 15-24's spending their time? Do you believe Twitter is going to trump Facebook? Does the next Facebook or Twitter already exist?

Share your thoughts.