Unsafe Load

Today as I was driving to work I was following a truck with lumber in the back.  The tailgate was down and there did not seem to be any type of tether on the load.  All I could think was that if he was ever hit (which is not hard on a busy highway) that the load would come flying out and hit whoever was behind it.  It surely would've gone thru someone's windshield.  !! 

I'm sure all they were thinking was that the wood wasn't going to shift while driving, but did they contemplate the possibility of someone else doing something stupid like pulling in front of them?? 

I stopped following right after taking the pic - which I took at a stop light.