When someone gets hurt behind your boat??

"The sound of some one knocking on wood" Nothing has happend to me but, I was wondering how this works, I would like to hear from real time experiances, Not I heard from a friend or I saw it on Opra, type of thing. What happens If or when someone gets hurt riding behind your boat ya know and its there own fault. I.E crash or somthing you had nothing to do with. Are your friends wrong to sue your insurance company? Do you make sure the people that ride behind your boat have there own insurance so they dont have to sue your or your insurance company.