In 1992 I bought a new GMC dually. While at work an acquaintance, not really a friend, asked if he could borrow it to pull his stock car to the races one weekend. Me, being a pushover usually, wanted to help him out but in the end I said I couldn't accommodate him so I said no, but I really thought about it. I asked a friend who knew both of us quite well about this situation, and he said this man just wanted to see if you would do it, but if I would agree he would take it. Obviously you learn as you go and now it would be a, "Get out of here jerk-wad."
I have a brother who is constantly asking to borrow things like a log-splitter, chainsaws, etc. because he says he only needs to use it once or twice. Not just from me but everybody who will accommodate him. He is a moocher, but then this is the same guy who has rental property, a huge gun safe stocked full of fancy guns, 3 brand new 4 wheelers, a new Harley etc. and then says he don't have money to buy the tool.
He has been over to our place once or twice over the last couple years and I never open the pole shed up and never walk him through it because he will give me a, "Can I borrow that." I have a two year old tractor and he has no idea I have it and I am going to keep it that way. I really hate to be that way, but I know his borrowing history and how he treats things. That plus he has a couple good incomes already.
But then I have a brother-in-law who really hates to borrow things and would rather rent the borrow. This is a guy who I would not hesitate letting him use anything because he keeps everything cleaner and in better shape than I do by far. But then, he is one who would never loan anything out either because of his views on others misuse of equipment.