Whenever people start doing this on a list I am on (obnoxiously post
off-topic messages) I take their addresses and use them when I am required
to supply registration information on a website.  Of course, I _also_
check those nasty little check boxes like "Send me email announcements and
news".

It is the only thing that makes putting up with inconsiderate people 
bearable - petty revenge, that is.

Of course, I am now going to have to do this for my own address...but it 
is worth the sacrifice.