Re: walking. If somebody shows me good footage of mid-foot walkers I might change my tune. Heel striking is very natural when walking and doesn't have nearly the amount of pressure or force that happens when one is jogging. I know a few people that don't heel strike but they also have some other issues in their legs. One of my friends has locked knees I think, and another girl walks almost literally on the balls of her feet but I forgot her reason why.
I don't see a need to alter the way you walk. I know some put babies as an example but I think it's only fair to use a baby/toddler that has gotten their balance down and walks without too much wobble and observe whether they strike heel-first or what. If you have to think about it too much, it's not natural.