perpetual motion violates a few fundamental laws of the universe...either a hoax (external power source) or simply a very efficient machine that will take a long time to stop. Either way, it can't go on forever without inputting some energy
That's ultimately the problem is that so far there hasn't been any evidence of being able to achieve over 100% efficiency. For example that is why you can't plug a gas powered generator into an electric motor that is attached to the generator and expect it to run forever as the motor takes more energy than it could produce.
yes, all you have to do is get the perpetual motion machine up to 88 mph
Seriously though, this is impossible. Having a perpetual energy source would be like having a freezer at absolute zero. Just because we can imagine a temperature in which all subatomic movement ceases, doesn't mean it can happen.
have you ever seen a perfectly built ball bearing? Those things can spin for hours and hours. The energy lost in that system is almost zero. However, some energy is lost, via sound and heat. Same with that magnet. Magnets lose their properties after a while. It might take a long time, but it will happen.