Well, I have deep gashes in my old Martin, just below the pick guard, almost entirely from one heavy handed strummer borrowing it one afternoon at the beach and flailing away using a heavy flat pick, missing the pick guard for the most part.   He did an amazing lot of damage in about 25 min. (total) of playing.   

OTOH, I'm grateful that several Mudcatters (Big Mick, Nancy, and Bruce, Fortunato and Susette, e.g.) and FSGW members offered to lend guitars for use by us out-of-town flyers at the Getaway and singarounds.   

I think the wisdom of lending guitars depends a lot on the setting and the kinds of people involved.   I'd rather my guitar be used by a lousy player who's gentle with her than with a hot shot who leaves gouges and dents.

Genie