Two separate experiences.  One I loaned out a leakdown tester and after a couple of months I wanted it back.  I called the guy and he had loaned it to somebody else.  Took a while to track it down.  New rules were created, if you borrow it your name went on the shop blackboard along with number and date.  If you borrow it you bring it back in the same condition, no excuses and in an agreed time period.

Second experience was borrowing a big drill bit for one project.  I broke his old already short bit.  I ended up buying him a new full size bit.  So, I ended up buying a nice new bit and still didn't have one.  No more borrowing after that.  (with minor exceptions and considerable thought)