In most states only one party to a conversation must consent to taping to make it legal. By contrast, planting a bug to eavesdrop on other people's conversations is illegal in most states except when done by law-enforcement agents with the proper warrants. A twist of today's technology is that it's far easier to record someone without their knowledge than to know if you're being recorded. Spy shops are filled with bug hunters, little devices that supposedly pick up signals emitted by recorders. None of those little 'debugging' gadgets work.
Sophisticated equipment used by professionals in countersurveillance can detect many spy devices.
The U.S. government has cracked down on the sale of hidden transmitters, which are illegal for civilian use. Last summer federal agents raided dozens of stores selling spy equipment. However, these tiny transmitters were hot sellers, and experts say there are plenty of other gadgets to take their place. A bigger concern is how socially acceptable eavesdropping has become. A lot of my clients are the owners of privately held companies or people in management in large companies.