I usually carry around my PSP in my back pocket. When I sit on something hard, like a bus or train seat, nothing happens to the screen. What just mindfarked me earlier today, is that a Cushioned Movie Theater chair can crack the screen.
Maybe you need to lose some weight :P
I weigh a wopping 148 Lbs. I'm waaaay too fat.
BTW Got the screen repaired today. Now I'll be able to play Peace Walker.