Except, if Google can break the data down by county, who's to say it can't also break it down by household? Despite the fact the company says it only gathers location data in aggregate, it clearly knows when you're home and when you leave home.
But it's still worth asking yourself whether or not we're really comfortable with the fact that Google knows this much about us, or more importantly, whether we want them sharing that data with the government.
In this case the data is public (meaning they aren't sharing it privately with the government only), and it's certainly useful