Someone's missed a point, but it isn't me. We already know no method is foolproof, I don't know whether I need to mention that twice or a dozen times before it's understood, but we're not talking about certainties, just raising the odds of keeping your average user banned.

Banning by domain of course is stupid, that doesn't even need to be mentioned. Yes, you'd "desenfranchise" all those Yahoo and Hotmail users. Users who have their own domains, where the method might work, are generally webmasters who aren't going to fall for it anyway.

Jason