Why is Facebook blocking tsu.co?

I read an article on Boing Boing about Facebook blocking links to tsu.co.

Then I tried to post a link to the Boing Boing post, and there was an error posting that. Here’s a screen shot.

I am surprised Facebook is doing this, I’d love to hear their side of why this is happening.

I posted a story on Facebook, with the screen shot above.