I'll chime in here and add that I was burnt by user 5810 to the tune of ~$550 USD. Two separate transactions and paypal closed one case almost immediately despite the initial notification stating that I had 7 days to respond. There was no explanation or note of any kind in the case.
I'm a long time member of paypal in good standing, not that I *really* expected them to take that into account.
The second case is still open and I posted any/all supporting evidence, such that I had. If I do get any serious response I'll update here.
About the same story for me too, #5810 took me for $541 across 2 transactions. The first dispute looks like it was actually generated by the "buyer" and the second seems to be automatically generated. The user-generated one looks to be closed (after I uploaded screenshots it was closed after about 2 minutes). The second is *still* open.
I'm not sure what the solution is, but people were talking about opening and resolving a dispute so that it couldn't be disputed again? I don't know if that works for PayPal, but otherwise intermediate escrow assuming the liability is the only "best for the seller" option that I can see.