Since then, the entertainment industry has put pressure on electronics manufacturers to limit the consumer’s ability to make copies. And as a result, many of the tens of thousands of products displayed last week on the Vegas expo floor, as attractive and innovative as they are, are designed to restrict our use.

DVDs are not so easily copied as videotapes. And the two rival formats for high-definition video on disc — HD-DVD and Blu-ray — are equipped with even more sophisticated copy-prevention technology.

Americans pay significant monthly fees to enjoy cable television, but cable companies also tightly control all of their content. They have been at war with electronics companies over the CableCard, a device that allows cable subscribers to record shows without having to buy a special set-top recording box. Cable companies want to make sure that the only way for consumers to get their hands on CableCards is to buy them directly from cable companies.

Even children are bothered by the increasing restrictions. One electronics show attendee told me his 12-year-old recently asked him, “Why do I have to buy my favorite game five times?” Because the company that made the game wants to profit from each device the user plays it on: Wii, Xbox, PlayStation, Game Boy or phone.

At this year’s show, the president of the Consumer Electronics Association, Gary Shapiro, spoke up for “digital freedom,” arguing that tech companies shouldn’t need Hollywood’s permission when they design a new product. Consumers, he said, should have the right to enjoy the content they buy at whatever time and on whichever device they like. They should also enjoy “fair use” to the extent that they can, without asking, copy movies for themselves, or copy a few seconds of a song and post it on a personal Web page.