I can't really say that I back either side on this argument but this certainly makes sense to me:

"No one would claim Andy Warhol plagiarized the original designer of the Campbell's soup."

"We just need Dean Kamen to create a dirt-cheap desalination system."

This is most definitely not the answer.
Desalination requires more energy and 'poisons' more water than it's ultimately worth. Desalination is to drinking water as Ethanol is to gasoline. A short term band aid to a much larger issue that keeps the masses quiet for another 50 years until those resources are found to be depleted as well.

If you are truly interested in becoming informed on this topic I hear this movie is a great source. Also, if you're down for a good read check out 'Blue Covenant' by Maude Barlow. Amazingly, informative piece of writing on the global shortage of water and how governments/corporations are stealing the water under our feet, literally.