In Garry Tan's survey, Tumblr is actually the most used site among all respondents. Tumblr is a blogging platform that lets users post things like text, images, videos, links, and audio.

But as Josh Miller wrote, teens seem to be using Tumblr mostly to look at photos from celebrities.

In addition to teenagers, investors have also shown quite a bit of interest in the microblogging site. Tumblr has raised $126 million to date and is currently valued at $800 million.

After feeling pressure from investors to turn the site into a real business, Tumblr flipped the switch on its first true monetization effort last year and generated $13 million in a matter of months.

Tumblr still has a long road ahead with monetization.