Would you use a gear sharing site?

Nope.

"Neither a borrower nor a lender be"

No.

Seems too sketchy with real gear.

no

Climbing friend,

No

I've recently begun writing up a little gear rental program myself actually, this is a very interesting thread to come across. I've talked with a few Lawyers, Home Depot and a University about rental liability waivers. In essence, personal climbing gear is no different than Home Depot renting a chainsaw to any swinging D. It all come down to a clean liability waiver that covers the renter, whom would not have any fault if something happened with his or her gear. Obviously, the gear needs to be regularly maintained and replaced if damaged or broken. The problem of gear getting damaged while being rented can be solved by a simple security deposit for each piece of gear being used. If it returns damages or broken, it comes out of the security deposit.

The fact is, there are many people (college kids mainly) that want to get into climbing/backpacking but don't have the skrill to invest in gear. The key is to find a reasonable rental price so that it's worth the renters while to rent instead of just buy their own gear that they will use one time.

Correct me if I'm wrong, which is VERY possible. I'm ready for rebuttals.

Somebody above mentioned gearcommons. 

I was intrigued by making some shared-economy cash off gear I'm not currently using, and put up some of my less-precious gear on that site. In 12 months, nobody has been interested in my pickets, haul bag, or tent. I don't know if there are any actual users there, but crashpads and other bulky stuff might make sense there.

Most people are still under the misconception that dropping a carabiner somehow breaks it (the metal they use today is perfectly fine even after dozens of 10ft+ drops onto concrete). It really is only a myth but until it is understood that you can't damage the gear that easy I don't think people would want to do it. (also how many of you out there have booty that you found on a route that you still used?)

Ropes imo would be more likely area of possible danger due to not knowing what has been done to it but still pretty minor, as long as you inspect it for bad spots / exposed core you are probably fine using it.

Kinda like gearlope.com/ ?