Inspired by AVForums, rather than having a list of account numbers / sort codes in the PM section, would it be possible to have a database for scammers.
For example, a system where those who have been blacklisted can be searched against new sellers. It may contain details such as their real names, ebay ID, email, address, bank details, telephone, mobile and any other people associated with them.
People who have been involved in scams would be on the system and you can compare that information against the database. The information will be protected and nothing can be added / deleted / seen by users. It would just flag up and you can contact a mod.