In a way, I have to agree with Tom, that if you are blasting you Wi-Fi strong enough that other people are receiving it, they should have a right to use it. After all, their own Wi-Fi could get interfered with because of yours. I know this to be true because in the dorms, people have all sorts of wireless printers and shit, and I can see like 20 things to connect to. As a result, the interference bogs down my own internet.
So they either need to make their signal strength weaker, or deal with me printing black pages on their printer.