I think that we need to be careful not to let articles like this stop us from drinking.

I read the same article in the Boston Globe this morning, and one of the things that jumped out at me was the quote "They found hyponatremia was most serious in runners who gained substantial weight -- 4½ pounds to 11 pounds -- from drinking lots of water along the route." I try to drink constantly as I ride, and I have weighed myself before & after exercise. I have never gained weight in the interim - I guess my combination of drinking, sweating, and exercising strikes the right balance.