Well, Steam's entire external connection went down, and at the same time a script-kiddie group started bragging about it on Twitter.
It IS possible that they were just lying. But in that case, it meant Steam lost 100% network capability to the game servers, the login servers, and the web servers, and has been down (for something like 3 hours now?) without saying anything. Last year, when they went down due to the overloading, it was intermittent support - try 20 times, get a response once. This year it was 100% up, then BAM! 100% down.
Either way, it's very annoying. How can I spend money on things I don't need if Steam is down?