I completely agree that out-of-office messages are useful and incorrect address messages are essential.
Spamcop is overzealous. It causes me no end of problems with my Yahoo groups because Spamcop identifies some Yahoo group posts (but not all) as spam and bounces them back to Yahoo. Yahoo then lists me as bouncing and I don't get any more list mail.
I complained to my ISP because this means that legitimate e-mails, that I *want* to receive, are being bounced without my knowledge.