Seriously old news... I attacked Facebook's 512 bit DKIM key back in 2010: http://blog.jgc.org/2010/06/facebooks-dkim-rsa-key-should-be...
It was on HN too, of course: http://news.ycombinator.com/item?id=1442385
I was surprised then that anyone would be using a 512-bit RSA key in the wild, let alone now.