My understanding and I could certainly be wrong-
The numbers on a light truck are manufacture numbers and not enforceable by local/state authorities. Local and state authorities can only require that your load be "safe" and that you are properly licensed to haul the weight.
Also- manufacture numbers/ratings are based on continuous duty. So to occasionally pull over the list weight or slightly over probably will have no affect on the long term health/reliability of your truck.
Most importantly, some people shouldn't haul any trailer let alone drive regardless of how much vehicle they have. Others can very safely tow a large trailer that exceeds the manufacture ratings... Use common sense and remember the responsibility you have to others on the road.
Finally- anyone who has ever seen an RV accident knows it would be impossible to gather up the yard sale that generally occurs and get a weight. :)