I was thinking a while back that spamtrap addresses should use shifting domain names; once (for instance) *@one.mydomain.com starts getting spam, you rename all the records for one.mydomain.com to two.mydomain.com, and so on. Then any spammer accumulating lists of addresses gets a gradually increasing number of bogus addresses that cost you no more than a DNS lookup. (Variant that costs you a little more DNS bandwidth: add a wildcard MX *.mydomain.com that ends up back at 127.0.0.1.) This doesn't do anything about the kind of spammer who pulls addresses of usenet (or wherever), spams once and then forgets them, though.