"I remember hearing this idea from well over 10 years ago," he said. "You walk down the street, you walk by a Starbucks, and your phone buzzes and says, 'Get a dollar off your next latte!' That's not even close to happening yet. But what the iPhone has done that is very much popularized, and has been made incredibly easy and elegant, is a way to derive value from your location."
Jeff Han, a consulting research scientist for New York University's department of computer science, who developed an interactive multi-touch screen that includes GPS functions, foresees a decline in GPS popularity due to privacy issues, after an initial surge in use.
"What does it mean when everyone can potentially point out where all their friends are?" he said. "Instead of actively calling all of your friends, you can say, 'Oh yeah, a few of them are over here.' So, that brings in social issues, and those are the things not yet worked out by cell phone companies.
"All of those things are being experimented, and I think that people will realize that they are giving up too much information about themselves, and there will be a little bit of backtracking," Han said.
Of course, use of GPS isn't all negative. One potential -- and perhaps obvious -- beneficial change will be cutting down on travel time. People will not spend long hours walking around looking for a hidden street if their cell phones can show them the way. Travelers will most likely feel more confident in new locations. Parents may give their children more freedom to walk by themselves at younger ages; their phones will take them home.
Knowles views the negative effects of widely-used GPS as intertwined with the potential for humans to expand their understanding of space.
"One effect of an increased dependence on GPS will be that peoples' ability to read maps will further decay," Knowles said. "Americans are generally poor map readers. Some cannot read maps at all because it's not part of our education.
"But what will grow, instead, will be better geographic imagination and awareness. People will see the connections between places more clearly -- not quite as accurately -- but will better imagine how to get from one place to another because of this technology."