I've been using eBay since ~99. Bought and sold probably 50 or 100 things over that time; so I'm hardly a power user, but I've never come close to being scammed. You have to keep your wits about you, sure, but it generally works pretty well.

It helps that I'm generally selling personal stuff I don't need/want anymore, so the risk is relatively low (I've only had a couple of expensive sales where I sold things worth over $1500). On the other hand, if I was a store where profit margins were king and a scam could really hurt me, I'd probably have a better system and better intuition about scams as well.