I've said it before: if we all do a little bit, it adds up to a lot. A recent article in the LA Times spells it out in another way:
The UCLA report, titled "Graywater: A Potential Source of Water," estimated that if 10% of Southern Californians implemented graywater systems for their laundry, showers, dishwashers and faucets, "the potable water savings would be equivalent to, or larger than, the capacity of a modern, large seawater desalination plant such as those proposed for California."
The article also points out the lack of education about greywater at the state level. I guess it's up to us to make sure we do it right. Do your research!