I just looked out my back window and remembered something that happened... About 4-5 years ago I moved a small shed out of my neighbors backyard. It required me to remove a couple fence sections and one of the 4x4 posts. When I put it back together, I dug down a little deeper and put a post back in with NO concrete. It was close to the middle of about an 80 foot stretch of privacy fence. This past December, when the tornado came thru, nearly every post in their yard was uprooted with the concrete still attached. The only post standing in that 80 foot stretch was the one I put in without concrete. And it was still straight and level.