A recent article in Slate basically said that it is safe to drink most stream water in the backcountry without filtering it. Turns out, this is not true. A few articles have come out discussing issues with the science reported in the Slate article. This one by Christie Wilcox is really good and worth a read if you are interested in science reporting or water quality or both.
Source: Backpackers, Don’t Listen To Slate: Science Does Support Stream Water Treatment – Science Sushi