I was thinking about all the fringe-science "Magnet Motors" and found myself reasoning thus: suppose there's a way to power a flywheel by slowly demagnetizing some permanent magnets. Wipe out the magnets' stored energy, and inject it as KE into the flywheel. If possible, this would explain a large number of bizarre PM claims, since every so often a basement inventor would stumble across the phenomenon. But as far as I know, nobody has tried to do this intentionally.
OK, what if?
First of all, a pair of repelling magnets placed upon a rotor/stator, if gradually increasing in magnetization, will experience net acceleration, and will only stop when the magnets get fully saturated. During each approach, they decelerate a bit less than they accelerate during retreat, so the flywheel receives a small kick. But obviously the magnetization requires an external power supply.
But the other way is interesting: *attracting* magnet-pairs, if slowly DE-magnetized, will be similarly accelerated. They accelerate while approaching each other, then decelerate less when retreating, for a net kick of KE. The net mechanical gain could possibly compensate the thermal losses of a simple demagnetizer section. I'll assume there's a few microwatts left over to keep a flywheel slowly turning against air friction. Very cool if true!!!
It's not hard to demagnetize a small patch on the surface of ceramic magnet by using a tiny supermagnet. Or, slightly demagnetize an entire magnet by using a coil to apply a brief pulse. Two supermagnets, if forced together with alike-poles repelling, will demagnetize each other. A simple flywheel couldn't do this, since attracting magnets tend to magnetize each other via "keeper" effect, which would lead to net braking. The mechanism needs more complexity. So perhaps combine a flywheel with a pendulum, or a flywheel with small parts rotating independently. Or perhaps just place a very tiny supermagnet at the right spot between ceramic magnets on the rotor & stator? Better yet, let one of the ceramic magnets spin, that way it will present a random spot of fresh ceramic for demagnetization.
I think it should be trivial to accomplish this for a few cycles (a couple seconds acceleration before the effect poops out, like unwinding a spring.) The real trick would be to juggle things so the demagnetization is repetitive but very very small, enough where it could keep a flywheel spinning anomalously for long minutes before the magnets weakened too much.
If these are feasible, I would suspect that similar fake PM machines already exist and would have been central to known PM scams. (The "Searl Device" suspiciously resembles one possible setup, where the patterns on the large central magnet would be slowly wiped out by the orbiting ones.) Such an effect could have been repeatedly accidentally discovered. Imagine owning a spring-powered wheel, but one where the spring is invisible and takes hours/days to unwind. Pranking possibilities! Perhaps even risk assassination by oil companies and the Illuminati! :) In any case, one could go online and start soaking investors immediately.