"To be honest, the fundamental difference between a camera bag and any other bag is really nothing more than just padding. If you forget all about the fancy designs, reinforced straps and weather-proof covers, what do you get? Padding. The padding of a good camera bag is what protects your camera and lenses from damage if you ever drop the bag. No, all that fancy quick-access zip locks or double-stitched straps, or even the weather-proof cover is not going to be of any help if gravity snatches the bag from your hands.
Check it out at TechARP.