This was a severe bug despite its misleading title, our users got only blank pages in IE and links did not work . It was pushed on a Thursday , then fixed some time by Monday, then next wednesday it was broken again, and a fix came a week later. [http://www.facebook.com/eggbuddies/posts/10150171378998545] Shit happens a lot more often than one would expect in facebook.
For a better treatise, read this developer's lament:
P.s. I laughed hard when i saw this video: http://news.ycombinator.com/item?id=2594083