Bill raises excellent points. In one, he refers to probiotics. It wasn't too long ago when all bacteria was considered "bad". As we learn more, we are finding that all micro-organisms aren't bad and some are not only beneficial but necessary. Our species evolved to live in the environment including all the micro-organisms. Since we are already discovering some of the beneficial micro-organisms, it isn't a giant leap to think there could be more. One can wonder whether purifying water in our municipal systems while reducing transmission of the really nasty "bugs" has also eliminated many/most of the ones we evolved to have in our bodies. Has eliminating these good bacteria, protozoa, etc... had a deleterious effect on our general health? Could many of our other diseases be a result (or made worse) due to having our intestinal flora out of balance? IIRC, our appendix served as a bacteria well to jumpstart our intestinal flora when needed. It became a vestigial organ as man started to live in larger and larger groups. We could then get our jumpstart just from being near others. With the constant purification of our municipal water, is it possible that drinking wild water could actually be beneficial to our general health? Is it possible this benefit outweighs the potential risk of "contaminated" water especially that which is found deep in the wilderness?