Actually, this is the argument that I don't quite "get".

jm01's wife wants to carry around a spare brake cable...I think that's smart. But...with hydraulics, you don't need to carry around a cable.

Carrying a cable out in the woods has nothing to do with the caliper and your bent piston issue. It would have been just as easy (or hard) for a pad to fall out of a mechanical as it was your hydro. I don't understand how the pad could fall out, though I don't have much experience with anything besides Avid. On Juicy's, if the caliper is around the rotor...that pad ain't coming out. If the pad is properly installed, it won't just fall out on its own.

You could bend the mechanical clamping mechanism just as easily (or hard) as you bent your hydraulic clamping mechanism (piston).

I'm not saying that in jm01's case he is wrong...I'm just saying that it's hard to bend a piston if you're using the equipment properly and installing it properly (on the Avids that I'm recommending). It's hard for a pad to fall out if it's installed properly. It's probably harder to accidentally rip a hydraulic hose off your frame than it is to break a brake cable.

The Hydro bonus? You don't have to carry brake cables around with you.