One way to implement something like that would be to have a fail safe break that uses electricity to pull a friction pad away from the blade when the machine turns on. Then when you shut it off, the brake gets applied, slowing the blade quicker than the friction of the bearings would alone. It would probably be safer to do that than to use energy to apply a brake because someone might be used to the blade stopping and get hurt if the power goes out.

So yeah, I agree that there should be something like that, now that I understand what you were referring to.