Ebay is indeed awash with scammers, but as a buyer you'll always get your money back providing you use a merchant like PayPal to pay for your purchases. Their insurance covers you. If you (someone) use a method which allows a fraudulent buyer to just reverse the transaction, you've only yourself to blame IMO.
But as a seller I'm not sure there's any 100% foolproof method of completely preventing scammers, no matter what you do, nor which service you use to sell your items (eBay, Swappa, CraigsList, etc). The most you can do is take the financial hit of advertising stuff as collection only, then insist on demo'ing it before the buyer takes it.
A few years ago, a guy on a hifi forum sold a £500 CD player on eBay to a buyer who subsequently claimed it was non-functional upon receipt, so the buyer returned it and pursued a refund action through eBay. The seller was 100% convinced the machine he received back from the buyer contained the non-functioning electronics of a different identical machine inside the outer case of the player he'd sold. I've no idea if he finally resolved that dispute to his satisfaction, I suspect not because how do you prove it? Potentially that experience cost him £500, plus listing fees, and all he had to show for it was a broken CD player.
