I remember one time I was looking at Tony Macalpine's guitar and he told me to go ahead and play it, I was like, whut? I of course gingerly and respectfully played it for just a bit. I forgot about that...
Also do you remember about 2 years ago or so someone stole Tony's gear when he was on a tour and they were asking publicly if anyone had a seven string in the area he could borrow. I would have loved to help him out in a circumstance like that... but do you loan your favorite?
It's kind of a tough decision you have to make. If it were someone I knew well and trusted, there would be a better chance. I'm not sure even a celebrity who needed an instrument for his gig, I'd let him borrow my guitar.
An amp or effects board I'd have no problem with. The guitar is a more personal thing that has a greater risk of possible damage in someone else's hands. How does one tell someone, "No, I'm sorry," when they're supposedly in need? How do say no to people when they ask for money or try to take something from you that doesn't belong to them?
This is where sometimes it's wise to draw the line between legitimately providing for someone and letting people take things from you by persuasion or force. I guess the question we might need to ask is, "Do you buy everything people pitch to (or try to sell) you?"
As I said before, I'd likely not lend anyone the use of my car for any reason, but I might not have as much an issue with them driving it while I was in the passenger seat, if I couldn't drive. (Just thinking of possible scenarios where this might occur). For example, if someone needed to drive me somewhere for medical help, or or home, after a medical procedure, when I couldn't drive.
But to review, I think it would have to be someone I'd personally known for quite some time, where we've both been to each other's houses, known their families, their likes, dislikes, values, etc. My feeling is that trust is earned, and no one really knows just how someone else might react in any given situation unless they've been relatively close friends with them for more than a few years.
That being well established, my buddy who had purchased my PRS SE A60E earlier this year has played all 3 of my previously owned instruments, but really not thought much about my FM9 floorboard unit. His preference is to play cleanly, and seldom does he use overdrive or effects other than a touch of reverb. With that in mind, I hope to create a separate preset designed expressly for him, that honors his preferences, when he brings his 7 string electric-acoustic over for a jam. We've known each other since about 2006, and although he's a bit touched with the gift for the unusually and uniquely silly, I kind of chalk that up to good meds and a wife who loves him, despite the warts.
Hope this answers your question, but if it doesn't, I'll be here again tomorrow to follow up on any additional questions you may have...