How much water is enough; or Your Lying Throat

Researchers have found that many athletes drink way too much water and some have died as a result. This is after years of them telling us we should drink as much water as possible. A couple years ago the leading kidney expert in the country did a study of the literature and found there is no basis whatsoever for the rule that you should drink 8 cups of water a day. How do you know if you've drunk enough water? You feel thirsty!! If you don't feel thirsty, then you don't need water! How about juices, soft drinks, tea and coffee, surely that's no good - you need pure water, don't you? Actually, those other drinks are over 99% water, so they're perfectly up to the task of quenching your thirst.
Another interesting aspect of the story is that the problem doesn't afflict "fast" runners because they have no time to drink that much water. Another way of putting is that only people who don't belong in the marathon to begin with are going to drink that much water.
It has always amazed me that people will force themselves to drink water. It seems so obviously stupid - like eating when you're not hungry, cooling yourself when you're not hot, warming up when you're not cold, sleeping when you're not tired. How could it be a worthwhile thing to do? Do they really think we've managed to have 6 billion of us walking around without a reliable mechanism to tell us when to drink fluids? Do they ever wonder how we made it this far without a bottle of water handy, or any potable water anywhere?