Well blow me down with a feather!
When hotmail.co.uk started I jumped in quick and picked up a couple of addresses which are my name. They pick up quite a few bits of spam even though I never got round to actually using them. Initials are just as popular.
Occasionally I take a peek to see what the spam-du-jour is and I noticed that the other thing that happens is that people randomly use that address when registering things or filling out forms. I sometimes reply if a real person then gets in touch, one of whom worked at a golf club and couldn't get his head around the fact that I was the wrong person.
I own a couple of spare domains so now everyone gets their own personalized version of my email address which is of the form:
Anything without "prefix." at the start gets "User unknown" which stops most spambots forging random From: addresses at the domain.
If I do get spam then I know who to blame and I can block that address whilst only affecting one person.
The random number removes the guessability factor if you know the prefix.