M:Metrics has released a study showing that young people use social media and other user-gen services disproportionately more than other age groups, which is hardly a surprise. Some stats to back it up, though:

The most popular category of user-generated content is phone-to-phone photo messaging, “with between 19.9 percent of American, and 49.9 percent of Italian teens reporting they sent a photo to another phone in the month of October”. Sharing video was also popular, and video messaging had a direct correlation with 3G penetration...which is good news for telcos trying to find evidence their huge investment in 3G networks was worth it.