I won't loan power tools. One time I loaned a decent B&D power drill (not a cordless) and it was returned to me completely burned out. LOL... it was like new when I loaned it out. Because of this I vowed never to loan out a power tool again.
Another time I loaned a pair of Wiss aviation snips to a guy I worked with. After several weeks of wondering when (and if) he was going to return them, I finally asked him for them. He said something like, "Oh, sorry! I've got them in my car!" I followed him to his car, and they were rusted up, in the trunk with the rest of his rusty tools. I never loaned him anything again.
I prefer not to loan tools out at all, but I have to remember the times when I needed to borrow something, so I usually do it anyway, considering who's asking. I do follow up, however, and make sure I get them back ASAP.
Years ago, when I was an auto mechanic (prior to the days when they became known as "technicians"), a fellow mechanic taught me this rule of thumb: If I have to borrow the same tool three times, it's an indication that I need to buy one. Unfortunately, not everyone follows this rule. For example, I was the only one in our shop with a complete set of Snap-On crowsfoot wrenches. I got tired of loaning them out, so I ended up just taking them home. I know, I wimped out on that one, but it was getting out of hand. In that sort of situation, you can't always afford to be a total dick, because a lot of things often require the help of others.
I now have pretty-much all the tools I'll ever need, with the possible exception of certain job-related power tools which would be seldom used at home. I try not to borrow.