It's not. Someone tried to rip us off on Paypal once. After they received confirmation that we'd shipped their product, they contacted Paypal, claiming that we'd scammed them, and demanding their money ($400ish) back. They got it, immediately and without any real question asked. As I'd already transfered most of the money out of the Paypal account, the amount I actually lost was small, but my account had a balance of negative several hundred dollars, which meant I couldn't use it for anything. It took about a month to get them to reset my account balance to zero, which is the point I stopped trying at, even though it still left me down the fifty dollars I hadn't withdrawn.
S'yeah. Paypal is pretty horrible.