It just does NOT make any logical sense to me to decide to filter the water because you have had an experience with Giardia. If you re-check the links I have included above, there is NO evidence that anyone has ever reported that links water in the Sierra Nevada with enough Giardia to infect anyone.
You can go ahead and filter or treat -- that's fine with me. But to condemn Sierra water based on your experiences leaves me completely baffled.
Oh get off it, already. If people want to filter, than let them filter minus the "peer" pressure, ridicule, etc.
Look, there have been bags of crap sited in or near every water source on the trail, so whilst folks are not likely to catch Giardia, perhaps they are not into munching down someone else's fecal matter.
