This might be the first nerd-blog post in a long time, so my apologies if I startle anyone. As a quick update, I wrote a book on security in Drupal and then founded a company focused on Drupal security services and then sold that company to Acquia where I currently work.
So....Tumblr is a big deal. They apparently have 120million users and are totally awesome.
Want to see the problem in action? I even made this handy dandy movie of the problem: