How much should you drink during a marathon?

It used to be that you could never drink enough during a marathon. However, recent studies found that at the end of Boston marathon, 13% of runners suffered hyponatremia, condition caused by drinking too much water. The runner who most likely suffered hyponatremia are those who drank over 3 liters of water and finished in over 4h00.

The recommandation of the American Medical Athletics Association is:

If you're a marathon runner, what can you do to protect yourself? The standard advice is to avoid guzzling more water than you lose in sweat.

I may had, the only time when I felt I was overdrinking is when I tought that I had to drink just as much water as I could to compensate for my loss of sweat. The truth is, the more you drink, the more you sweat. The only true way I found to gauge my drinking is to listen to my body and drink when I feel thirsty.