At first, this and this about the Census Bureau using GPS to record the coordinates of every household in the U.S. might seem like tinfoil hat talk. And, it would be great of one of our favorite "debunkers" treated it as such, because the fundamental are actually true. Let's turn to this NPR report from July 31, 2006 (link):

Two-and-a-half years from now, in early 2009, the Census Bureau plans to send an army of 100,000 temporary workers down every street and dusty, dirt road in America. They will be armed with handheld GPS devices.

Robert LaMacchia, head of the Census Bureau's geography division, says they'll capture the latitude and longitude of the front door of every house, apartment and improvised shelter they find.

"We will actually knock on doors and look for hidden housing units," he says. "We will find converted garages; from the outside, it may not look like anybody lives there."

1. A picture of the unit is here. It might be possible for census workers - including those from groups like ACORN - to get the data in some way. That might involve simply inserting a memory chip or a simple hack. I don't know the specifics on the unit, but it probably wasn't designed against such attempts.

2. Various factors can contribute to GPS being slow, very slow, or inaccurate. I'd imagine that the same problems getting a reading in a canyon would contribute to problems getting readings in the city versions of canyons.

3. The article indicates that some want to change the laws to make the GPS data publicly available.