Facebook (News - Alert) achieved a significant milestone in October, topping one billion users — a feat that deserved plenty of discussion on its own. However, a recent survey from the Pew (News - Alert) Internet and American Life Project, along with Harvard's Berkman Center, has shed some light not only on its use, but also on that of other social media, such as Twitter (News - Alert) and Instagram.

Specifically, the survey covers U.S. teens and their social media use. For this study, "teens" means youths aged 12 to 17 years.

For starters, 95 percent of teens use the Internet, while 81 percent use social media sites. Of those teens who use social media, 94 percent reportedly have a Facebook profile. By comparison, the second-most used social media service, Twitter, was used by 26 percent of teens in 2012. However, Twitter experienced the most significant growth of all social media, more than doubling in use from 2011, despite reports of teens staying away in droves.

Instagram was the third-most used in 2012 with 11 percent of teen social media users, while all other social media included in the survey were used by 7 percent of teens at the top of the range — MySpace (News - Alert) and YouTube — down to a mere 1 percent by the likes of Gmail, Pinterest and Meet Me.

As for Facebook use, the study shows that network size is fairly even, with over half of teens reporting fewer than 300 friends and 44 percent saying they have more than 300 friends. This results in the average number of Facebook friends being 425.4.

Even though many parents may complain that their kids spend all their time at home on Facebook, the study suggests that teens with more Facebook friends tend to be more active. Those teens also tend to use a broader range of social networks aside from Facebook, as well.

Other parental fears regarding social media use — bullying and privacy — were found to be fairly minor issues among teen Facebook users, with 52 percent reporting a positive online experience, while most are actually very careful about what information they share and with whom. Indeed, while teens in general were found to be more open online than in 2006, they tend to spend a lot of time managing their reputation. This seems to vary according to gender and network size, however.