We all like to think that we know people well enough to be able to trust them, but when it comes to money (or prospect of money from lawsuit), one never knows.
I may have shared this story on the board before. Short version: a family friend pledged his assets to help an old friend (30-40 years of friendship) secure a business loan. This old friend then disappeared with loan money. The guy who pledged his assets lost everything and committed suicide, leaving a wife and kids to grieve and without a roof over their heads.
My parents shared this story with me when I was young as a lesson to never trust anyone when it comes to money, and I've never forgotten it. If you can't trust an old friend, who can you trust?
This partly explains my paranoia about liability. I would like to think that my riding buddies won't sue me if I lend them my bikes and they crash, for example, but I just don't want to take that chance.