An email address for every site

I wrote this advice to a friend on the topic of alternate email addresses used to sign up at various sites:

By the way, a cool trick that I picked up somewhere is to register an account at http://www.cjb.net. You pick a subdomain of cjb.net (like joeblow.cjb.net) and then they redirect any email that goes to @joeblow.cjb.net to an email address of your choosing. So what I do is I have ilowe.cjb.net and every time I sign up somewhere, I give an address that encodes the name of the site I am registering on (for example yahoo-groups@ilowe.cjb.net). This has two benefits: first, I don't have to give out my real email address; second, if somebody starts spamming me using one of the addresses, I just add a filter to my mail client to kill that particular address and continue along my merry way. That way I don't have dozens of sites pointing to one "junk" email address that I need to log into every once in a while to clean out.