Re:This only punishes the foolish (Score 3, Informative)

Actually there is another feature of Gmail that was advertised through their blog. And it states that [e-mail] is directed to [e-mail]

So basically all the characters after the + sign (including it) in the email address is stripped to determine to receiver. You will see that the email has been sent to [e-mail] and then can filter on it. If used intelligently, it can tell you which site is selling your email address to other 3rd party companies.