Interesting. More infographics in the article itself.

The sites included in this survey are: Facebook, Twitter, LinkedIn, Pinterest, Tumblr, Reddit, Hacker News, Slashdot, Github, Stack Overflow, Orkut, Quora, WordPress.com, Blogger, Flickr, Myspace, Tagged, Hi5, LiveJournal, Yelp, deviantART, StumbleUpon, Goodreads and Last.fm.

What I learned about age

55% of Twitter users are 35 or older. The average user is 37.

63% of Pinterest users are 35 or older. The average user is 40.

65% of Facebook users are 35 or older. The average user is 40.

79% of LinkedIn users are 35 or older. The average user is 44.

Only 2% of all social media users are 65 or older.

55% of Tumblr users are under 35.

58% of Reddit users are under 35.

60% of Github users are under 35.

Hacker News has almost half of its users (44%) in the 18-24 age bracket.

More than half of DeviantART’s users are below 25.

What I learned about gender

17 out of 24 sites (71%) have more female than male users.

Most male-dominated site? Slashdot (87% males) is the standout, followed by Hacker News (77% males) and Stack Overflow (76% males). In general, the more tech-focused sites in this survey have more male users than female.

Most female-dominated site? Pinterest (79% females) is in a league of its own, followed by Goodreads (70% females) and Blogger and Tumblr (66% females).

Facebook and Twitter have the same gender distribution: 40% male, 60% female.

The only sites in this survey with more male than female users are Quora, Reddit, Orkut, Github, Stack Overflow, Hacker News and Slashdot.

Growth Hack: Choose a social media site that most represents your desired type of user, and customize your application for that site.