Interesting stuff Andey. I knew that those shaded pole motors could overheat, and burn out the windings even, but I hadn't seen them as such a fire risk. I would hope that the rising current as sections of winding shorted would blow a fuse or trip a breaker in most cases, but it certainly justifies the thermal fuses we often see now.
Regarding pond pumps, I've messed around with those and found that you can even pull the rotor in and out whilst it's energised with no discernable effect on the stator temperature. I agree with jraef that the winding impedance limits the current to a harmless level.
