@ “porky” : It also comes in contact with a lot of surfaces in the collecting and bottling process. These surfaces may or may not have a lot of bacteria on them that can multiply in a closed container, such as a plastic bottle.
@ pete: i think it may have something to do with the particles from the plastic leaching into the water. freezing #1 and #2 plastics is not a good idea, because it can cause leaching of carcinogens just like heating them up.
Remember the Nalgene scare? The same stuff (BPA) and a lot of other much icker crap is in #1 and #2 plastics, and it leaches out much more easily, which is one reason why these plastics are sold as disposable, not as a reusable container. they are not meant to be frozen, heated, or used more than one time.