When is weight distribution needed?

lenr wrote:
....snip.....put the shorter poles on top close to the front to increase hitch weight. Pulling out on the interstate he swayed across 3 lanes--thankfully no traffic. He got settled down and then swayed all the way to the right berm where he stopped. We now think that too much tongue weight contributed to the sway. .....snip.......

You think?

I was hauling a load of steel sheet piling on a beaver tail trailer behind a dump truck when I had to let up on the accelerator to maintain enough front tire contact for steering. A WD hitch was not available for that combination, but common sense and scales were. The guy gave us the piling, so I took more than I should have. That's the moral of that story. Anything can be overloaded.