This will deter some, but I suspect the commercial spammers will soon get round this. Not all sites have such a user. Your message should include all the junk mail's headers to aid proper diagnosis. Often spammers have accounts with ISPs which prohibit such behaviour, and it is fairly common for these people to lose their accounts in enough people complain. Before you send the complaint, make sure the junk mail's headers confirm the origin of the mail first.
Spammers are notorious for using fake email addresses.