No need for the old sock trick, the Georgia Institute of Technology has a news release (in handy pdf format) that they have just started working on a method to block surveillance cameras.

The current prototype uses visible light and two cameras to find CCDs, but a future commercial system might use invisible infrared lasers and photodetecting
transistors to scan for contraband cameras. Once such a system found a suspicious spot, it would feed information on the reflection’s properties to a computer for a
determination.

“The biggest problem is making sure we don’t get false positives from, say, a large shiny earring,â€? said Summet. “We need to make our system work well enough so that it can find a dot, then test to see if it’s reflective, then see if it’s retroreflective, and then test to see if it’s the right shape.â€?

Once a scanning laser and photodetector located a video camera, the system would flash a thin beam of visible white light directly at the CCD. This beam – possibly a laser in a commercial version – would overwhelm the target camera with light, rendering recorded video unusable. Researchers say that energy levels used to neutralize cameras would be low enough to preclude any health risks to the operator.

Nice that they worry about our health, even though they use rather absolute terms (“any health risks”). They also suggest a few markets, including silver screen digital rights management:

Stephen Fleming, Georgia Tech’s chief commercialization officer, said motion-picture groups are actively looking for technology to foil piracy. Movie distributors might even promote cameraneutralizing systems by refusing to send films to theaters that don’t install anti-piracy systems.

I can see a hot new fashion trend in movie-going circles: retroreflective lens-shaped earrings.