I have more gear than I can use, so I actually wish I could lend out my older/heavier gear more than I get the chance to. If I've gotten more than a decade of use out of it and it's second-string now, sharing the usefulness and facilitating someone getting outdoorsy easily outweigh stuff-protectiveness for me.
For my more recent/ultralight/precious stuff, (Quarter Dome, i'm looking at you,) I'd have to be confident that the person's at least as overly careful and detail-oriented as I am. That conjunction of request and person hasn't happened yet.... 🙂
I've shared my jetboil, water filter, sleeping pads to a variety of friends.
Jetboil came back fine - just used gas without replacing which is what I expected.
Water filter came back fine - they even cleaned it because the instruction card said how to.
Sleeping pads - one was a Sea to Summit self inflating they didn't know how to use. Still waiting for that to come back.
But overall if I'm not using it - I'm happy to loan it to someone I know who might need it. I usually buy gear with the best warranties so I feel pretty confident it should last for friends to borrow.
sharing your gear can either work great or turn out horribly wrong.
If you backpack a lot, you wind up with several of everything...as you march down the road (pun?) to getting lighter and and lighter.
the problem is - the road to 'lighter packs' is lined with VERY EXPENSIVE stuff!
I loaned my Tarp brand 'Notch' to a relative in California for our trip to Bridger Wilderness, never got it back.
My hiking buddy loaned her very expensive "under quilt" (used by hammock hangers), and she is still waiting for it to be returned.
Stoves are not cheap, pads are expensive and need to be treated with TLC (a popped one will ruin a trip!), same with bags, chairs, and electronics.
Pots, water bottles, last years pack and some purifiers are pretty durable and can be loaned without worry.
If you haven't paid for it, you probably will not treat it with the TLC needed for very expensive, lightweight, critical equipment. I say critical because, the more you hike, the longer you stay out, and the farther you'll get from the trailhead, therefore all your equipment is critical to your safety and well being (hypothermia, injuries, etc..)
I guess a lot of it depends upon the trust you have in the person.
for what it's worth
REI member since 1979
Don't lend things unless you are prepared for them to get damaged, dirty, lost or just not returned. If the item is extraneous consider just giving it. If you don't trust or like the person enough that you would lend them the money for the item if they needed it and not care too much if you got it back then don't lend them the item.
I have lent my best gear to my adult kids with good results although they are not quite as good at cleaning and maintenance as I would like. I figure if it does get lost or broken I'll get to hear about their adventure and getting new gear can be fun.
Sometimes a lent item comes back better. I have a giant family tent I lent to the parents of one of my kids friends and it came back in a new REI duffel!