The Modern Lighthouse
A reader points out that the new iPhone takes advantage of the modern equivalent of this externality:
"Every Wi-Fi access point, whether public or private, sends out a signal every second or so, like a lighthouse. We pick up those signals and use our technology to calculate your exact location."
What Skyhook does not do, Skyhook Vice President Shean says, is connect to those Wi-Fi networks. "We're detecting, not connecting."