One of the young guys at work asked me to lend him a rifle for deer hunting the other day. I've lent out guns before and had them returned in poor condition. Ruger Red Label came back with rusted out chambers earlier this fall, the guy looked at me and said "Oh geez, sorry." Some people don't understand, or put the same importance on these things. I was a bit hesitant, but lent him a new, unfired Ruger #1 45/70. Slapped a low power scope on it for him, and he bagged his first whitetail this weekend.
Its unfortunate when people don't look after borrowed items properly, but I'm at a point where I'm not going to lose sleep over these things anymore. In reality, its just metal and wood. It contributed to making his first deer hunt a success, and a ding or scratch pales in comparison to that.
Just my two cents, and I'm pretty anal about taking care of my firearms.