Actually you can get robbed also using paypal ? And all other payment methods. Ok paypal can refound you taking the money from the account that robbed you , but do you think that after taking your money , the thief will leave the money in his account just for paypal to return them back to you ??
That's why there is reputation on ebay , because also using paypal you are not sure to receive what you buy.
There is also the possibility to be robbed when using cash actually.