I have purchased 3 cars on E-Bay sight-unseen and had good results all three times. The KEY things you can do to protect yourself are:

1. Ask lots of questions and get pictures of everything (engine bay and underbody as well). Be detailed. You likely will
    not get a chance to see the car before you pick it up.

2. Do expect even with a successful purchase to find minor issues with the car. These are, afterall, being sold 95% of
    the time by wholesalers who picked them up at auction.

3. Always do BOTH Autocheck and Carfax. These will give you as much info as you can get. They will give you info you
    can use to do further research.

4. Once you have the Autocheck, you'll know where the car has been. Use the VIN to call a dealer and see if they can
    provide you service records, or the name of the dealers who have sold, resold or wholesaled the car. Often a simple
    phone call will yield records of repairs, scheduled services performed by the dealer and even sometimes a manager
    who remembers taking the car on trade or purchase and the circumstances. Dealers are generally very helpful when
    you tell them why you need the info. You won't get the previous owner's name, but you can get a lot of good info
    on the car's service and condition. You may have to make a few calls, but it is worth your time to talk to folks who
    have actually seen and worked on the car. The service dept is the first place to start.

5. DO NOT LEAVE FEEDBACK until after you've received the car and had a chance to find out the bugs. If there is
    something that was not mentioned that you asked about that needs fixing, most reputable e-bay sellers will work with
    you.

Always remember that you are buying the car AS-IS and that most cars will have minor things that need some work, especially if the car is more than a couple of years old. Don't expect a showroom car for a wholesale price, do your homework and don't be afraid to use this awesome place to save yourself a couple of thousand $$$. If you take care of yourself you'll be very satisfied and happy and have a few more $$ in your pocket. Many of the sellers get the cars from wholesale auctions for well under trade-in value and you can benefit from their work and get the same deal. They want to sell their cars quickly and with a minimum of fuss, so you can get a great price. I picked up an 03 Nissan Murano SE AWD with 22k miles on the ticker (in perfect shape) for $18,900 here. Try getting that ride at your local car lot and see what you'll pay!!!!

Good luck and happy hunting. As folks say, if the deal's too good to be true, it usually is, BUT, you can expect the deal to be better than you ever dreamed if you protect yourself.