Understand why you feel that way. However . . . this situation would be an unfortunate, but rare occurrence in consideration of the number of transactions that take place on eBay each and every hour, day, week! There are always going to be crooks out there to take advantage of the innocents (me too!). But, remember, it's not just eBay (internat buying) where people get screwed. That can even happen over the counter at your local auto parts supplier.
My only advice: Check, ask lots of questions, communicate with the buyer before, during and after the sale, ask for more explicit contact details, etc. If they aren't interested in giving you the information you want, move on and find another seller/buyer, or deal with on-line companies who have too much to lose from bad publicity.
We've probably all had bad experiences . . . learn from them, and hope for no repeats.