Re: the precedent this sets if a manufacturer can
Remember the Sony Playstation update that removed much-loved OtherOS functionality?
I have to say that Samsung are in a hard spot here. Suppose they *didn't* take steps to render safe these devices, when they have a mechanism to do so. Are they then liable for increased damages? I bet you can find a lawyer who would say so.
A better change might be one that destroys the ability of a battery to hold a charge (maximum chargelevel := 1%). The phone would still work when connected to an external power supply, then. Maybe there's no way to do that with an over-the-air update.
Afterthought: you're never going to get 100% of phones turned in for refund, anyway. How many have been stolen, or dropped in the lav.?