Just after the release of the Mann vs. Machine rumours, Valve posted the following statement earlier today:
"Last night we launched our most fiendishly difficult ARG (Alternate Reality Game) yet, involving roughly 5000 individual pieces of data that had to be painstakingly collected and decoded by equipping specific items and then performing even more specific actions in-game. It was diabolically, even needlessly complex, and there was some concern among the TF team that this time we might have gone a little overboard. It would take the community weeks to sort through this, we worried.
We shouldn't have. In just twelve hours, the master-class code breakers in the community put their collective brainpower to the puzzle and cracked it wide open, uncovering a mysterious link at 2:46AM PDT this morning that promised a small taste of things to come in TF2. We couldn't be more proud of you guys. Also, if we're being honest, a little giddy at the possibilities, because if you can apply yourselves this commandingly to a goofy online puzzle for a war-themed hat simulator, next time we'll think big and ask you to construct a manned space shuttle to Mars or something."
We won't spoil it for you, so to read the comic you can click here.