Tumblr is growing--fast. The site's founder, David Karp posted  Quantcast's latest figures  on the Tumblr staff blog, saying that its 170 million worldwide visitors had propelled it into the top ten of U.S. blogs. And, like Zuckerberg  before him, he pronounced himself "humbled" by the experience.
Tumblr's many gems include this  and this . And you just know that this  is going to spawn a Tumblr spin-off. When serious news organizations  are getting in on the fun, and Tumblr becomes a place to shelter from the storm , you can see why it's shooting up the ranks.
[Images from that old chestnut Selleck Waterfall Sandwich ]