A whole bunch of Valve's source code seems to have been stolen, including Half Life 2. The forum thread with the pics in question.
"Inside you'll find what is at the time of writing, over 600 heated posts regarding the legitimacy of a leaked "Half-Life 2 source code", a thread that has reached nearly 60,000 views. A huge number of people now have their hands on this code, there is clearly no doubt that this code actually exists, the doubt lies in what it is, exactly....."
And from the forum...
"We've ( the hl2.net staff ) managed to get our hands on a copy and can confirm it's real. Funky stuff, shame it was leaked though."
Gabe Newell has posted on the halflife2 forum, revealing what looks like a very elaborate source heist!