Windows on an iMac?

When I wasn't grilling Apple folks about .Mac integration I was talking to them about the possibility of running Windows on some of this newly release hardware. To a person the response I got was, 'Windows can't be installed.' When I pressed for a reason, whether it be hardware or something else, no one knew.

I know that Apple didn't release this cool gear so that people could install Windows but it seems to me it should be possible. How many days do think it will be until we see an iMac running Windows?