I'm sure if you're a huge scammer they'll do whatever to catch you, but usually if you have a negative balance they'll just sell your debit to a credit agency and they deal with you.
Paypal is all about screwing the seller. I have not had a Paypal account for a couple of months now and I am all the better because of it. As a seller you are never safe because even after your Paypal account is closed a crazy customer can come after you and Paypal will give them advice to call the cops and harass you.
"As a seller you are never safe because even after your Paypal account is closed a crazy customer can come after you and Paypal will give them advice to call the cops and harass you."
Paypal Legal Action? 
