Are Seattle police using Wi-Fi to spy on people?

The Seattle Police Department has installed a new wireless mesh network, paid for by the Department of Homeland Security, in the city's downtown. A local alt-weekly, the Stranger, is questioning whether the Wi-Fi network will be used to track the movements of people via their mobile devices:

How accurately can it geo-locate and track the movements of your phone, laptop, or any other wireless device by its MAC address (its "media access control address"—nothing to do with Macintosh—which is analogous to a device's thumbprint)? Can the network send that information to a database, allowing the SPD to reconstruct who was where at any given time, on any given day, without a warrant? Can the network see you now?

Unfortunately, the answers to these questions aren't yet clear, because police declined to answer many of the Stranger's queries. However, the paper's research seems to indicate that the technology can be quite easily used for these purposes.

You can see evidence of this mesh network the next time you're down in Seattle. Just pull up your phone's Wi-Fi settings; the Wi-Fi networks in question are named after the city's intersections.