I ended up buying a backpack for my camera gear (Kata 467) a few months ago. I loved it, it was well made, comfy, and a nice size for short hikes.
Anyway, I was out for a hike and I walked under some low lying branches. One of the branches got in-between the two zippers on the back of my backpack, and as I stepped forward, the backpack opened and my camera gear fell out.
LUCKLY it fell onto some snow and not a bunch of rocks. Nothing was damaged, but the lenses and camera body surely would have broken if they fell on rocks.
After this scare, I decided that I never wanted this to happen again, and started using a "real" hiking backpack when out for hikes, similar to this: http://www.rei.com/product/797504
This ever happen to anyone else? With the popularity of photo backpacks, I'd be surprised if it hasn't.