Anecdotally, I've not yet heard of any backpacker using the AM drops having any illness issues and FAR more use the drops than tablets because they're less expensive. I'm sure they don't follow the directions really precisely either. Some even premix a day's batch worth to save time, especially if in a group setting. However, I also think the danger of infection in the wilderness is overblown, which is why you rarely hear about people getting sick.