You know, I read that whole thing from the BenzWorld forum, and one thing doesn't add up:

An RFID chip is pre-programmed, and it would have to be pre-programmed before it was inserted in the fob. If so, then the actual programmable part of the RFID process is in the car - not the fob. Which is why you can program a brand new key to work with your car - all by yourself - with the method posted above.

The car doesn't program the RFID in the fob, it reads it and puts it into it's own "accept" list.

So, why is it that we can't make the ebay key fobs work? Hmmm...