I've known about and used the showroom code for a couple years, but vowed to my OA that I would never spread it all over the internet. This is a horrible thing to blast out to the masses. I implore you to remove the post from here. It could have simply been sent in a PM.
Once some smart@ss gets wind of this, they can go into a showroom and turn-off the showroom mode on all the cars. Then, customers can blast the radio to 11, lay on the horn, spray other customers with washer-fluid, fill the showroom floor with water from the A/C creating a slip/fall hazard, and (if the key is close enough nearby) run over other customers.
If this code gets leaked-out, Tesla will remove (change) the code for the safety of the people in the showrooms, and the few of us who use it legitimately will be without.