Those who drink unfiltered water from natural springs are taking a huge risk.
Some won't believe me, others rely not having had a problem in the past and some will rage at reading this.
None of this however, will change the fact that Giardia and Cyrptosporidium cysts are widespread throughout the world, including the US.
Filters are extremely small nowadays and very effective. I hope some of you will consider using one.
-Tim-