First there were security cameras, sprouting like mushrooms on street corners and buildings. Then came shopper cards, offering discounts in exchange for details about buying habits.

In recent years, we’ve seen the emergence of electronic tags or “cookies” on the Internet, software that monitors e-mail, GPS devices that pinpoint our position on the planet, and a growing number of machines that capture finger- and face-prints.

Now comes the news that federal regulators on Wednesday approved the injection of microchips under the skin, enabling physicians with the right gear to know who someone is without having to ask. And yesterday, the omniscient-seeming search engine Google bested itself by announcing a service to probe for information both online and in your own machine. One company official called it a “photographic memory for your computer.”

Google says no personal information will be sent back to the company. But if it feels like you can’t do anything these days without someone looking over your shoulder, you’re not just paranoid. Cheap computers, blazing fast networks and clever engineers are finding more and more ways to keep tabs on where you go and what you buy, generally with your permission. They’re even getting better at guessing what you’ll do next.

“It’s this whole new world. It’s sort of like all these little details about our lives are being recorded,” said Richard M. Smith, an Internet security consultant in Boston. “We love the conveniences. We love the services. But people kind of instinctively know there’s a dark side to this. They just hope it won’t happen to them.”

To be sure, companies have long gathered personal and shopping information to better market to customers, often with dubious results. Who hasn’t received junk mail or telemarketing calls that seem to have no connection with their lives? But those initiatives are fast improving and accelerating as people live more of their lives tethered to cell phones, the Internet and the rest of the wired world, where trading off personal information is part of the price of admission.

More here.