Right I've considered everyone's responses and discussed with other admins and we will allow negative trust. I don't agree that keeping items someone sent you in error is stealing or that it necessarily makes you untrustworthy (though it does make you an asshole, no doubt.) But, I hear you all when you say that it does matter to you and it's something you'd want to know. End of the day, trust doesn't stop you from trading with someone, just gives you some background to inform your decision.