I stick to purchases under $200 on eBay and do seller research before buying. I haven't gotten burned in a couple of years (got a dead laptop battery from China), but I was only out $25 and I just ate it. I just stick to old, maybe-working or untested-but-probably-broken electronics that I can usually fix and small items like video game cables.
I stopped selling years ago when they bought Paypal and changed their policies to not allow negative feedback on buyers. Having gotten out of the coin-op amusements business and having nothing left to sell helped that decision along as well. While I was a seller, I only had a couple of bad transactions take place where the buyer wasn't happy or didn't read the description properly and they were required to return the item before any refunds were issued- again, before the policy changes. If I have anything to sell, I usually sell locally through Craigslist, meeting in a public place to do any transactions.