Well there aren't any.
Lets assume you empty your PP, then the buyer initiates a reverse charge. PP go to your account, see the funds aren't there, and push you into the negative.
At this point, they try and recover the funds from you - but guess what? You're under no legal obligation to put anything in there. In fact, Paypal can't do anything to make you.
Lets assume the seller, does a runner and is blacklisted by Paypal. This would surely mean that he can no longer use Paypal (his name and address is blacklisted) and can therefore never use ebay again, given that most sellers only accept paypal (cheques and bank xfers are risky for the buyer)?
If the buyer can no longer use Paypal, then I would much rather take the financial hit, to avoid the blacklisting.