@Jaakko Holster: firstly, I’d like you to read “this comment”:http://www.alistapart.com/comments/gracefulemailobfuscation?page=2#14.
Secondly: sure, according to the official RFC, a plus sign is allowed in e-mail addresses, but:
a) In reality, e-mail service providers don’t allow users to create addresses that contain a plus sign (!)
b) I’m perfectly aware that ‘plus addressing’ is an interesting and commonly used technique (by geeks, at least) to tag/filter incoming mail and/or to backtrace where spammers got your address from, but these are not the addresses that you publish on a public website; you use plus addressing when signing up for online services, newsletters etc. Don’t forget that the plus sign is *not* a part of the actual address.
c) However, if you insist, you *could* very easily adapt the regular expressions that the GEO technique uses, to separate the name/domein/tld in an e-mail address with something else (a ‘/’ would be a good idea).
I hope this helps ;)