The idea might be fine, but what if someone tells you: "this man is scammer" and he was in fact just pissed off by that guy. What I mean, you should be careful not to put innocent man on list.
Other problem is that scammers can always use some other addresses, like the one of their relatives, etc.
How about making a "white" list (though I would prefer orange;) ) that would contain only trusted persons.
