In the never-ending debate between blogging and micro-blogging, Tumblr usually gets lumped in with Twitter and Facebook on the micro-blogging side. But Tumblr is actually somewhere in between the status bursts of Twitter and Facebook and the long-form publishing of Wordpress-style blogs. If anything, it is more accurately described as micro-blogging than Twitter or Facebook because you actually produce short blog posts filled with images, links, and videos. But the key to Tumblr's incredible growth—it's adding a quarter billion pageviews a week—is how easy it makes it to post something and reblog what your friends are posting. Tumblr CEO David Karp recently sat down with Chris Dixon for a Founder Stories interview in which explains how he started Tumblr four years ago as a reaction to other blogging tools out there. "All blogs took the same form," he notes. "I wanted something much more free-form, much less verbose." People wanted to express themselves and blog, but he felt that the standard blogging platforms available at the time—Wordpress, Blogger, TypePad—were too complicated. "These tools I just don't think worked for most people. It's a commitment, you need to sit down for an hour and hammer out a post."