True enough for when it falls out of the sky and onto the catchment area for your locale, but anything further than that starts to involve an energy cost and by extension, a relevance to conservation. Now the water itself still is unlimited for a while on a local or national basis, but eventually your aqueducts and ground pumps are sapping water from places which can ill afford it - see various Middle East countries for examples of this, as well as in the south west USA.
The other source is corporations wasting water on our behalf in the pursuit of the cheapest cost approach. Do you really think a 40inch LCD TV would cost as little as it does to buy if the companies were conserving water, energy, and other materials, and cleaning up all their waste afterwards? Guess that's why they don't build them here (N America, W Europe, ANZ) any more.