Tumblr debuted in 2007, but it wasn't until 2011 that it exploded in popularity. According to comScore, Tumblr grew from 4.2 million visitors in July 2010 to 13.4 million visitors in July 2011. That's a 218% increase in 1 year.While the vast majority of Tumblr users are young, it's safe to assume people from more diverse age groups will give Tumblr a try in the near future. Currently 50% of Tumblr's active users are under 25 years of age.
Are you using Tumblr yet? If not, you can follow the links to learn about Tumblr features for bloggers and how to make a free blog on Tumblr.