There's an old saying amongst Argentinian Gauchos and Indians: "Never lend your knife, your horse or your woman to any man." .
There are very few people that I would trust with one of my knives, in fact I think I'd only trust my dad and perhaps a few guys from my traditional leatherworking class. Something they all have in common is that they already carry their own knives. I think my dad has only borrowed one of my knives three times in my whole life, and not because he didn't have one of his own but because he wanted to try out my latest toy.
I've lent knives to a couple of friends in the past, they were luckily never damaged but a couple of times I thought my friend would cut off a finger. People are just not used to properly sharpened knives.