What year MBP is it? I used to carry my 09 MBP around in a backpack with textbooks. It had some issues with the SATA cable failing often. One Genius had a theory that the design of the SATA cable in the unibody MacBook Pros would not stand up well to that kind of transporting. I'm not 100% sure that's the issue, but it's something to be aware of if you have an older 13" MBP.
As for general damage to the case, using a sleeve might help. If you have a newer retina MBP I'd recommend the sleeves from Rickshaw Bags. They're some of the only ones I could find back in 2013 that were designed for the rMBP. Incase made excellent neoprene sleeves for the older MBPs, but last I heard they hadn't designed new ones. Maybe the new retina MacBook will get them off their butts.
I'd also suggest making sure the camera and other things are in separate compartments from the MBP if you're using one bag. Then there's a little protecting rather than everything just bumping together in one compartment.