Anti-Valve site No-Steam claims to have hacked Valve, gaining access to internal web pages, customer credit card information, Valve financial and error logs and the company's Cafe directory.
No-Steam's owner MaddoxX claims to have also posted code which he allows will let people create their own cafe certificates. MaddoxX also posted what he claims are a series of files "to valve cafe, including a few CC numbers and some info's." - From http://kotaku.com/gaming/hack/rumor-valve-hacked-cc-numbers-stolen-253598.php
I got a chance to download the files and to take a look at the code itself. It turns out that they have really been hacked. I cant release most of the pictures because they have people's credit card numbers on them. However, here is a safe pic to show that the hacker took.