Once so a friend could take a girlfriend shooting, he only owned one gun then, they brought it back right after finishing up at the range.
Once loaned my Savage to a friend so's he could go deer hunting with his brother in Mississippi. He had it for a bit. I don't hunt currently (yet for some reason own a scoped bolt action .30-06), so getting it back ASAP wasn't exactly a priority. It is sleeping soundly in my safe right now.
Loaned my 92fs to a third friend who only owned revolvers, so he could practice to get his CHL (in Texas, if you qualify with a revolver, you are not permitted to carry a semi-auto.) He liked it so much, I ended up selling it to him.
Loaned one to a co-worker for his shift. Odd circumstances the night before he was unaware of, he didn't bring his, and I wasn't working. Got it back the next day.
Now all of these folks I consider friends, I trust them, and have been shooting with the first three multiple times. A casual acquaintance? Not a chance. I might take them shooting if I think they possess the requisite maturity. At least while handling firearms.
