Rich Kids of Instagram is #1 ?!

Besides that one, Texts From Dog (#7) and Staff (#12) are the only two in the Top 15 I have heard of.

The average Tumblr user has 108 followers.

I linked to this article from the "Tumblr Is Not What You Think" article:

http://pandawhale.com/post/17018/tumblr-is-not-what-you-think-techcrunch

Here are the most visited Tumblr blogs worldwide, according to Quantcast:

1. Mcupdate.tumblr.com (1.9 million unique monthly visitors): A blog dedicated to news about Minecraft, a game about blocks. 
2. comoeumesintoquando.tumblr.com (1.2 million unique monthly visitors): A collection of hilarious GIFs.
3. dedalvs.tumblr.com (1.1 million unique monthly visitors): The personal blog of David J. Peterson, the guy who created the Dothraki and Valyrian languages for HBO's Game of Thrones. 
4. onenable.tumblr.com (715.6 thousand unique monthly visitors): A site dedicated to Korean comics.  
5. theworstroom.tumblr.com (707 thousand unique monthly visitors): A blog about the trials and tribulations of finding housing in New York City. 
6. publicshaming.tumblr.com (645.7 thousand unique monthly visitors): Created by producer Matt Binder, Public Shaming will call you out if you start tweeting hypocritical content. 
7. siriuslymeg.tumblr.com (606.3 thousand unique monthly visitors): A blog all about movie quotes and inside jokes. 
8. howdoiputthisgently.tumblr.com (525.3 thousand unique monthly visitors): A graduate student documents her life through GIFs.
9. comedycentral.tumblr.com (490.7 thousand unique monthly visitors): Comedy Central's official blog. 
10. reasonsmysoniscrying.tumblr.com (449.7 thousand unique monthly visitors): A blog that documents all the reasons why children cry.

Source: http://www.businessinsider.com/most-popular-tumblr-blogs-2013-5