drinking

Has anyone one see these (or better yet used one)? Kinda a neat tool that filters dirty water and allows you to drink it without getting sick. Great for hikers or even your bug out bag. http://lifestraw.com/products/lifestraw/

We've all heard or been told to drink 8 - 8 oz glasses of water a day. Or, then even some people started getting scientific by saying take your body weight and divide by 2 to get the number of ounces you need to drink. Well, what if you been told there actually isn't any scientific positive...