You are not worrying over nothing believe me. Stalling the cutter (and probably blowing the mill's fuse/cb) is arguably much more likely than a power cut and under those circumstances, the pf will continue to drive the work into the stalled cutter.
At that point, several things could happen:
1. If you have a rotating head machine, said head will be forced to rotate out of the way against its locking nut. Recoverable but you're faced with re alignment which is difficult without destroying your setup
2. The pf may simply stall and/or blow its fuse/cb (if you're lucky)
3. Potentailly the pf could burn out its drive motor if you don't get there to switch it off in time.
All of this means that you tend to feel you have to "babysit" the machine. It would be nice if the machine manufacturers foresaw this (particularly if they are the ones offering the pf for their mill) and included an accessory outlet with appropriate switching.
Ask me how I know all this. 
I did start a thread on this topic here a while back if you're interested.
Edited By Sid Herbage on 17/06/2013 01:49:13