Normally depends on the situation you got scammed, like if you brought digital goods i know its a real pain as paypal turn around and say it cant really be proved either way. If it was for an item you have a tracking number for etc and returns are accepted then you can just return then item, prove you done so with tracking info and you will be refunded, as the seller wont have a leg to stand on. Paypal with you 100+ something days to do it i believe.
if that isnt an option then i have heard of people going down the route of 'unauthorised payment' etc, as in a child or someone in the household had access and made a mistake, someone actually charged back on me after i sold them fifa coins via ebay, and they used that excuss and got away with the item and a refund. There are ways around it, just got to be a little sly as paypal are little **** when it comes to stuff like this