Everyone’s Facebook feed is pretty much the same as everyone else’s of the same age. Twenty-year-olds pose in the club, 30-year-olds share wedding photos, by age 40 you’re looking at a lot of cute pictures of your friends’ kids. But with Tumblr, you never know what you’re going to get — even with people you know personally. That, in a nutshell, is the difference between a social graph and an interest graph.

via Why Tumblr Was a Massive Steal for Yahoo – Adam Rifkin – Voices – AllThingsD.

Here’s an interesting tidbit from TechCrunch written Feb 2013.  From Tumblr Is Not What You Think

Pop quiz: what is the favorite social networking site of Americans under age 25? If you guessed Facebook you are way behind the eight-ball, because Tumblr now enjoys more regular visits from the youth of America. That figure struck me while reading Garry Tan’s January 2013 survey and I wondered why? So I delved deeper; this article describes what I discovered while exploring the Tumblr network.