Thinking back on this subject, I've been in the room for most of the abuse performed on my guitars. Typically it's somebody who owns some plywood P.O.C. that they mysteriously left home with the "hey can I use your guitar for a minute?" or they just pick it up without asking. I've had really expensive guitars come back with a hatcheted headstock (cool old 70's Hamer without any previous scars), covered in pancake syrup (solid rosewood/spruce acoustic) and then there's the unmistakable sound of your guitar hitting the floor while it's plugged in to your amp (oh cr*p is that MY Guitar!)...good times
Since I've never been reimbursed or even had that offered, I now carry guitar case keys on my key ring.