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