I'm no expert, but the signal that leaves your computer travels through many many obstacles before it gets to HTC's servers. If any one of these is interrupted, you will loose that link with the server and get discoed. There is no way for the game to know where that link was broken, whether it be somewhere in Oklahoma, space, or at the back of your computer. Sure, some people could show a bumpy status before a disco, but that's not always the case, a person can have a "legitimate disco" and be completely cut off. A disco can be initiated by simply pulling the cable out of the back of your computer (that big phone line, or regular phone line if you're on dial-up). I don't think Alt+F4 counts as a disco.
