Spam is one of the reasons I'm using such address - since I give an unique address to every website, it's easy to see if somebody works with spammers. Also, given that eg. GMail allows you to use + address extensions for quick filtering, I'd have expected that people writing e-mail address validators would get their act together. Guess I expected too much.
As somebody on thedailywtf said: Programmer thinks he needs to validate an e-mail address. "I know," he says, "I'll use a regexp!" Now the user has a problem.
BTW, another problem with the forum: trying to paste anything in the editor places the pasted text at the very start of message, not where the cursor is.