Earlier quoted context omitted.
I used to do this. The amount spam of mail I received to mailbox names I had never used started to dwarf my actual email. This is apparently made worse because spammers take the fact that these addresses will receive mail as a signal that they're valid, causing them to send more mail to them. A couple of years ago, maintaining the blacklist passed the point where this was a viable technique for me.
This is why you might consider maintaining a white list or white pattern instead.
It has the advantage of being able to spontaneously create email addresses when signing up for things, while still blackholing most guessed addresses.
I like this idea a lot.