I had to get a new key for my '91 300E last year. The dealer made me show up in person (an hours drive) and show proof of ownership and a picture ID. This Info along with the VIN was sent to Mercedes. The dealer told me that since Mercedes got some negative publicity about car thefts that they had clamped down on the key replacement process.

I used my Insurance card with the VIN number on it and my driver's license for proof.

In addition to having to go to the dealer to order the key, I also had to go back to pick it up and go through the same process again. They will not mail it to you. I think the cost was around $22.

I don't think dealers or anyone else can circumvent the process because they have to make copies of your documentation and send it to Mercedes.