I don't like borrowing from people. I always worry if something should happen. My sister and I loan a lot but she's my sis and very reliable. We have cats and when I loan her a book she hides it from her cat, who loves paper.
I don't mind loaning to anyone who is reliable and I know who those people are. As WMU said you have to know the other person very, very well.
I would loan my friend and neighbor anything. She takes meticulous care of everything. She's an example of someone I trust.
Same with another neighbor, who uses our tools once in awhile. He's a great guy and everything comes back pristine.