The biggest threat, I think, is the number of companies that still have XP sitting behind the corporate firewalls. If you get a foothold into a corporate network, you can basically own their entire IT infrastructure with decade-old hacks that were addressed years ago. While corporate world is pretty bad, I'd have to say the healthcare industry is far, far worse off.

They were always hit with every type of malware possible, but ths time MS just wont issue out any new patches.