I've been an ebay seller for a while now, and have two accounts going. One seller account and a private one.
In the last six months, and among other things, I've sold a Nikon F5, an Nikon F3 and a Nikon F90x. About £500 worth of books, and many other items including paintings and artwork etc.
I've also bought a lot of photography gear off there, and many, many books lol!
One of my brothers even bought a BMW off there last year!!!
I've had no problems, and I don't know personally anyone who has. You'll always get exceptions, but it's the same in whatever method of shopping you use!