****PLEASE READ......YOU MAY LEARN SOMETHING******
I have purchased several Applecare products from ebay. All have registered just fine and I have never needed to use any of them. I also purchased a brand new Macbook Pro that had Applecare included....It was a great deal!!!
Well..... I sold my Macbook Pro and purchased an iMac. I tried to cancel my Applecare from the Macbook Pro. I called Apple and they said no problem,,,, until they looked up my Applecare. It seems my Applecare was purchased from an Apple store 2 months before my Macbook Pro was even manufactured. Apple had no problems refunding my money just not to me. The refund would go to the person (credit card) that purchased the plan from Apple.
Apple asked me for proof of purchase, which I did not have since it was purchased from ebay. I told the rep. that I purchased from ebay and the response was..."ebay is not an authorized Apple reseller". I know that you do not need to be an authorized re-seller to buy or sell Applecare, but it greatly reduces your chances of getting scammed!!
BOTTOM LINE...... ANY APPLECARE PURCHASED FROM EBAY THAT DOES NOT HAVE A BOX WITH SERIAL NUMBER IS NOT VALID.
Macman812 claims he sold over 30,000 Applecare plans (written in an email response to me) and never had a problem with Apple. His rating is the best you could get from ebay. He is very convincing that he is an "honest" seller. There are thousands of "satisfied" customers that will post on the forums on his behalf. There are plenty that post about how they used their Applecare plans purchased from him. Your lucky, Apple hasn't caught you yet and they may never. In my case it appears that the Applecare that was sold to me was probably purchased using a credit card that did not belong to the seller (hint...hint).
Remember Applecare is about protecting your investment and wallet for a definitive piece of time...it is not about passing the registration process and receiving a certificate of insurance and a copy of Tech Tools. At anytime Apple can invalidate your "warranty" if they discover that it was ill-gotten (keygen'd, shoplifted, or fraud credit cards).

Something to think about......If I were a crackhead and someone was willing to pay me $25 for every Applecare box I can "reallocate" from an Applestore I would be the happiest crackhead in the known crack universe.
To All that are thinking of purchasing an Applecare Protection Plan from ebay OR purchasing a laptop/iMac/iPod/iPhone or iwhatever with Applecare PLEASE READ THIS POST AGIAN!!!