Nielsen just released the Social Media Report 2012 (more data here). Here are a few things to note:

Facebook remains the most-visited social network in the U.S. via PC (152.2 million visitors), mobile apps (78.4 million users) and mobile web (74.3 million visitors), and is multiple times the size of the next largest social site across each platform.  The site is also the top U.S. web brand in terms of time spent, as some 17 percent of time spent online via personal computer is on Facebook.

-More than 70% of Pinterest’s users are female.

-The top three reasons by far for why social networks users become connected/friends: know person in real life, interested in keeping up, mutual friends. This is more evidence that social networks are mainly about maintaining existing connections rather than creating new connections.

-Watching TV is increasingly linked to tablet, smartphone, and Twitter usage. Multitasking is alive and well and perhaps TV can be interactive after all.

There is also some fascinating data at the end about social media usage around the world.