I know most people are discussing guitars and similar instruments but I often take my piano (yep, a nasty tinkly thing, lol!) to music nights. It is not that heavy but, with the case is damned awkward to lug in and out. I have some great mates who always help if they are there but sometimes have to manage it, the stand, my accordion, etc, which is a bit of a pain. I don't mind people using my piano,(it is an electric creature with less personality than other instruments, I own, ) if they ask, but I do mind people just getting up, playing it, without asking, then sitting down, and...then watching me struggling to carry it out at the end of the night, without offering to give a hand, or at least saying thanks. People wouldn't go and help themselves to someone's guitar without asking, well not usually, anyway! As for my accordion, no one ever asked to borrow it, (ok ok accordion jokes..........!)but I think I would feel very uncomfortable and not happy about lending it out unless I knew the person well and that they would play it carefully. It is fairly fragile and would not stand up to being knocked. Someone once asked to borrow my saxophone, yeuckkk! I made the excuse that I had a bad cold, (I didn't) and said, no. Some people are really thick skinned and oblivious to reading vibes. I wouldn't dream of asking to borrow that sort of instrument, bleughhhhh!