Didn't read through thread.. Sorry if I'm restating anything..
Anyway, this sounds like a great idea, but sadly; I disagree. Ok, this database would be good, someone simply uses the search feature and see if that specific address has charged back before. Good in theory, in actuality, no.
Problems?
Keeping up with the list. It would be mods only (in that specific section) and Globals. Allowing everyone to edit it could lead to it being deleted entirely. Saying that, very time consuming and mods should be putting their efforts in other things - scam reports - that need attention.
As well, it's SO easy to change your PayPal email. All you do is press "change to primary" and click the link they send you in an email. All the work would be in vain, or at least a strong majority of it.
/Tl;dr
Noz from meh.