I read somewhere on the web that the diuretic effects of coffee were due to the caffein preventing absorbtion of water. So drinking more water to counter-act the dehydrating effects of caffein would only result in increased urination.

On the other hand, I read somewhere that if your body becomes acclimated to the caffein, then this diuretic effect is lessened.

Think there's any truth to that? I don't really know where to look for authoritative answers to this kind of stuff, and you can't believe everything you read on the web, that's for sure.