There aren't that many scammers on eBay - but the ones there are tend to be greedy. This means that they will always try to pull their scams on high-value items like cars and computers, so that they can make a lot of money quickly. Since buyers generally buy these items very rarely, they may not know about the various scams out there.
With cars, you will generally find that scammers try to get you to send them money in advance, for whatever reason. For some reason, some people aren't all that reluctant to pay 50% or 25% of the money before delivery using a relatively insecure payment method, especially on a car. They reason that the seller will obviously deliver it, as they'll want the other half of the money.
But there never was a car! Pictures of cars aren't hard to find, and the experienced scammers will have a whole library of pictures of different cars. The seller just got your $5,000 for nothing, and you can leave them all the negative feedback you like. They'll just go and open another eBay account and find their next sucker.
While it's not an outright scam, what you might find is that the car does turn up, but simply doesn't live up to the description - it has been oversold, in the tradition of used car dealers through the ages. If this happens to you then you should open an eBay dispute and say your item was not as described - you might get a partial refund.
If you bid in a computer auction but