Ian over the past 4 years i have bought lots off ebay a car 3 bikes laptop 2 comptors and loads of other stuff.
I have also sold lots too.
Never had a problem. As long as you check their feed back ratings and phone them up get a landline number and address you should be ok.
I usually find by talking to them on the phone tells you if there genuine or not.
If you can you should always go to see what your buying if its an expensive piece if kit, other wise if distance is a factor you take a chance.
Dont forget on ebay there are usually loads of pics so you can see what your buying,if you get down there after the sale and find that the vehicle is not how its been described then you dont have to buy you can refuse.
Paul