I am not talking about already established members/members who already know the meaning of a signed message or how to read it. Scams mainly take place with newbies. Very rarely I have seen established members getting scammed. The scam accusation boards are filled with claims from newbies.
Some don't know the meaning of escrow/signed messages/account sales. They get scammed mainly because of the trust or by an old account that's trusted. I know that it happens very rarely as mainly accounts are bought for Signature Campaigns but some are bought to scam as well and this has been proven to be true as well. A person can go about editing/deleting all his previous messages which reveal the original account holders identity and in that case, a signed message would not work. It would be only theymos who could get back the deleted messages/edited comments.
Do you have any examples of this? It seems that most scams are attempted by low level accounts and accounts that are unlikely to have been purchased.
If you can't get a signed message for any reason then it would probably be best to have that person send first or to use an escrow service to protect your money