So since this topic has never been discussed before......lol
The last 3 comments from mkirsh, Kayteg and burningman sum it up and are probably the 3 most "to the point" posts on this website I've seen in a while!
Those that believe the absolutes of the "yellow sticker" are fine and conservative....to a point. It is not by any means an absolute, but it could be in the right scenario.
Some people are very astute, experienced, mechanically inclined and maintain their vehicles well and the other end of the spectrum are completely inexperienced, don't maintain their vehicles for squat and wouldn't know of the engine was getting ready to window the block until a connecting rod hit them in the shin.
Then there's the other group who know they "can" do something but are more secure or simply wish to have a large factor of safety or want the ultimate in comfort level/driving experience.
Combine all this together and the "right" answer for you is not going to be the "right" answer for someone else.
To those that can sort through all the factors intelligently, you can safely haul more with less. To those who can't or don't, please "buy" your factor of safety up front rather than building it yourself. And to the chicken littles, kill a bus load of orphans if you don't buy a dually, please think before you speak!