I was replacing the brakes so I had one side up on the jack and I had the car on neutral but the car was running and I saw the rotor move. I was certain I didn't have Limited slip differential. should my wheel spin on neutral? the wheel was off and if I gave the car some gas the rotor would move faster.

 

Great, you were running the car while changing the brakes? Does this seem sensible to you?
There is sufficient drag in the tranmission to transmit motion, that's why the rotor was moving. If you want to keep all your body parts DON'T run the car while it's jacked up!

 

That is just completely insane your lucky you still have fingers or you hand or arm or face for that matter.

and you don't put your car on nuetral you put it in neutral but that doesn't really matter it just sounds funny to me.

 

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It just ocurred to me that this is probably the reason most workshops won't let the customers inside the work area. Probably afraid that the customer is going to climb in and try to start it while the mechanic has his hands inside the engine bay removing the serp belt or whatever. All becomes clear, now..