HA! Same thing here! I jacked up the rear driver-side, (tire was still on - I was just testing how it all worked) marveled at the weirdness of it all, and I noticed that the car started to "fall" back! I was able to support it by holding the jack straight, but how on earth could this be deemed a safe system to change a tire?

My old, cheap Nissan has a simple little jack that cranks up, and supports the car wonderfully. This big, supposedly well designed luxury car has this cheesy pole thing, that hooks in crooked, needs a piece of wood under it, and oh yeah, bring some wheel chocks so the car doesn't collapse on you! WTF????

I'm thinking of buying a cheap hydraulic jack to keep in the trunk just in case. It seems like a real PITA and unnecessarily dangerous to change the tires which is a very basic thing.