It all depends how you approach buying and selling on Ebay. I have over 700 transactions and have only had one go bad on me, where a cheque was returned due to no funds 10 days after showing cleared. Guy went bankrupt so no chance of collecting on that one.
Check out who you are buying from very carefully, use
www.toolhaus.org/cgi-bin/negs to check for negative feedback. only buy from a genuine trusted seller, the rogues are easy to spot.
When selling do not accept bids from anyone who has not registered a credit card with Paypal. Also keep an eye on who is bidding and check out their feedback, do not accept bids from anyone with less than 5 feedbackswithout them contacting you first.
If an the price looks to good to be true it usual is! Common sense goes a long way.
I find Ebay still the best market place by far.