My standing order is if I'm going to hit something yell otherwise don't say anything and your wasting energy waving your arms around. I know what i'm doing, it may not look like it but I do.
Though I would agree that this forum must have all the greatest backers in the country because from my experience as a driving instructor and trailer towing trainer the majority of the people I see have a hard enough time backing up a vehicle much less a trailer attached to the vehicle. It amazes me how anyone over 25 years old hasn't figured out how to use the vehicle mirror then there are the guys that think there cool by only using there mirrors and not all there viewing options.