That link is to a medical study of backpackers and diarrhea. For those who are curious, but lazy like me, the take home message from the link is: you can get diarrhea if you fail to treat your water, but don't expect that to be enough; you also have to wash your hands "post defectation" and keep your dishes clean.

These would seem like common sense, but it is always nice to see common sense backed up by hard numbers.