Always wondered about that? I have seen some really shaky setups on top of cars and trucks. We almost lost 2 surf boards last summer because I trusted my kids! Imagine being a car behind that situation - mayhem!
I thought I was doing the responsible thing. I had a J-bar kayak rack and all. It's hard to tell what let go first and what followed, but by the time I pulled over the kayak, straps, and one J-bar were all gone.