@Kristin: With it being so prevalent in raccoons, and the eggs being so hardy, I wonder if baylisascariasis isn't more common. Maybe it just rarely causes obvious problems? Maybe it commonly eats away at the part of the left parietal cerebral cortex which causes people to fail to realize they don't really need to carry a heavy pack? :)
@Ryan: I agree. There are raccoons in the areas I hike (Appalachians and foothills), although I wouldn't say there are significant numbers. I guess I just don't like the Russian roulette approach to water safety. The water is most likely clean, but there might be a raccoon latrine just upstream too.
@John: True, good point.
@Matt: Right, different situation in the high mountains... unless maybe mountain goats and marmots can be carriers of any dangerous worms?
@Laurie: My perspective exactly. The risk is enough to make me choose filtration over chemical or UV. I don't like adding chemicals to the water anyway, and I'm skeptical of relying on electronics with batteries. The admittedly small risk of baylisascariasis or even a less dangerous worm is enough to sway me toward filters over other methods. Btw, I just got a Sawyer Squeeze filter which is 4.5 oz (wet weight, including dirty bag). That's heavier than chemicals, but around the same as UV, and tastes better than chemicals.