The blades pivoting won't really save the heli. If it happens in flight, it really makes it easy for a boom strike to occur. Having a blade fold back a bit also throws out the balance of everything going on, making the heli go totally out of control until the blade straightens itself out, but that will take several rotations. During that time, the odds of a boom strike are way up, and the heli is going to be vibrating like crazy, trying to shake itself to bits. I could easily see that kind of vibration taking off ball links or trashing electronics.

Also, just about any time you touch the rotor blades to something hard at high speed, you almost certainly bed up the main shaft. Hit hard enough, and it's easy to strip the main gear a bit as well.

In a real mid-air, I wouldn't rule out a bent flybar as well, which would lead to a crash.

Rotor blades are actually really fragile, and the forces quite high, so that when a blade hits something, the forces acting on the rotor head, mainshaft and so one are huge, well beyond what it's designed for. It's not the movies, where hollywood effects sometimes make it look like you can chop things up with a heli's rotor.

Now, on the foamie side, foamies fly just fine with cuts and holes in the wings. I've had prop cuts during combat matches where the other guys prop put 3-4 cuts clear through the wing, and the plane didn't even notice. I've had BIG holes torn out of wings and kept going as well.

Here's a couple of pictures after I got in to a mid-air during 2548 class at Nats. You can clearly see the amount of the wing that has been cut up. I flew this plane around, turned, and made a normal landing with it. This is a bit extreme, but it did fly. Now, with a flying wing, getting an elevon knocked loose is much worse than loosing an aileron on a conventional plane, and will make the plane basically uncontrollable. However, pulling back the throttle and pulling hard on the elevator will slow a foamie flying wing down to the point where it really won't be hurt at all when it hits the ground.

http://www.wheek.org/airplanes/2007/07nats25.jpg
http://www.wheek.org/airplanes/2007/07nats26.jpg