Oh, don't worry, I'm paranoid about making sure everything is tied down tight after I narrowly avoided a dancing ladder that fell off of the rack on some moron's pickup on the freeway.
I too am paranoid about following vehicles, generally sedans or soccer mom vans, with the hitch mounted bike carriers - but for a different reason.
Most of these seem to be overloaded and have a harmonic bounce, back and forth in some kind of rhythm, as the car/RV goes down the road.
IMO, a simple strap running from the top of the rack back to the top of the trunk or ladder would stop this harmonic bouncing.
I know not seeing the bouncing would make me feel safer.
I just don't trust the shanks and other metal parts on these carriers to not develop cracks or weak welds because of this shaking.