A web hosting customer of ours sent spam today. Stupid? Yes. But it gets better. He paid a lot of money for someone to send the spam (thousands of emails), and we (his web hosting company) were on the spam list. His site was gone less than a minute after the first spams arrived. Even better is that we have control of his .uk domain so he can't instantly redirect the domain elsewhere.
Now sending spam to your web host is extremely stupid, but I'm sure you can all tell stories of even greater stupidity ... please tell, I'd love to hear them :)