Prick Advisor and ex shamingWatch
The intent is clear, to provide a forum where all 'bad' men are listed so that all women know to avoid him. But I see a problem where we decide what 'bad' means. In cases of convicted criminals, I see no problem listing them (though I have issues with the effectiveness of that), and even where the accused is not convicted but an allegation was made to the police, I think that's probably okay (though they open themselves up to libel). However, where people are reporting on things they didn't report to the police, or even non-crimes, I take issue. If someone really is that bad, you need to at least try to get them locked up rather than hope everyone joins your Facebook page and boycotts him (or some more extreme form of vigilante justice).
Then we have the obvious issue of false allegations. It is not unheard of for a bitter ex to spread false rumours about someone, and this is essentially a kangaroo court. As before, I don't think there's an issue know people's criminal histories (but you should probably dump someone who has attacked you straight away rather than bothering to check their history first), but unverified allegations with such personal details about their subjects is dangerous to someone who is innocent until proven guilty.
There's also a concern for the posters' own safety, but I think they're old enough to take responsibility for themselves. If they want to call out a violent thug who hates their guts wanting to kill them, then that's stupid but an adult decision.
What do you think of such groups? I think it has the same issues as Clare's Law, but also includes the possibility of false allegations and even vigilante justice, as it was set up to go around the official legislation without solving any of its problems.