Round 2 of Tumblr vs. Wordpress vs. Blogspot: FIGHT
Adam Rifkin stashed this in Blogs!
Tumblr is closing in on WordPress in unique visitors, and it is now tied with WordPress in monthly visits. It kills WordPress and Blogspot in time spent on site.
What's most interesting is that 9gag has more monthly visitors than all of them: http://pandawhale.com/convo/990/9gag-has-67-million-monthly-unique-visitors-and-2-billion-pageviewsmonth
And Reddit and Imgur are competitive, too, though they're closer to the WordPress range than the Blogspot range.