Cameras are a feature of the digital age that are bound to increase in their presence and create new controversy. London in particular has experienced a wave of discussion about their extensive use of security cameras on the streets and in other places. New York has done something the same, watching for terrorists. It is easy to plant cameras and they can be very small. The latest is the embedding of cameras in billboards. If you stop to look at a billboard, it can take a measure of your age, gender and the length of time you looked and send the data back to a database. The manufacturers say it doesn't invade privacy because it doesn't take your picture. Not everyone agrees. In any event they could take your picture with a few minor modifications. We will see more of this. Computer monitors and televisions could easily have built in cameras. Some monitors do and TVs and monitors are converging. Lamps? Furniture? It's an issue that won't go away anytime soon. Billboards That Look Back - NYTimes.com