That probably can't happen. However, having a dedicated account for paypal that you keep minimally funded prevents paypal from grabbing money in the case of a dispute if you sell. For buying I fund my paypal purchases with a credit card. That is the safest way to do it. Then if you have a dispute with the seller, and paypal doesn't side with you, you can open a dispute with your credit card company.
I see what you're saying...I've had so few disputes issues, but it's a good precaution to cover all bases, for sure.