For those of you that have answered "never", how many have let their kids or other loved one ride in a vehicle with someone else driving? Most, if not all I bet. You trust the lives of your loved ones in other's hands, but a material object like a firearm is off limits?
Worried about liability? Not unless you loan the firearm knowingly to a felon or have a reasonable suspicion that they are going to commit a crime with it. Otherwise it's no different than loaning them your lawnmower. Like the lawnmower tho, if you loan it knowing there is a safety issue with it, you can be sued for neglect. It's pretty much just common sense. You don't lend a gun to someone with mental disease or limited mental capacity. You don't lend your gun to a crackhead or a wife beater. You don't lend a firearm to someone with no knowledge of firearms. You don't lend great Grandpa's pristine 1895 or any other collector grade firearm to someone who just needs a hog gun for the weekend. If your friendship or family member is not worth the value of a readily replaceable firearm, one needs to re-evaluate their priorities in life. If you can't trust your friends or family members enough to lend them a readily replaceable firearm, I feel sorry for you.