Dr. Liebowitz, a professor at the University of Texas at Dallas, said the problem on the Web today has less to do with monopolies or software design than with intellectual piracy, which he has also studied extensively. In fact, Dr. Liebowitz used to be a favorite of the “information-wants-to-be-free” faction.

Image RETHINKING THE WEB Jaron Lanier, pictured here in 1999, was an early proponent of the Internet’s open culture. His new book examines the downsides. Credit... Jeffery A. Salter/The New York Times

In the 1980s he asserted that photocopying actually helped copyright owners by exposing more people to their work, and he later reported that audio and video taping technologies offered large benefits to consumers without causing much harm to copyright owners in Hollywood and the music and television industries.

But when Napster and other music-sharing Web sites started becoming popular, Dr. Liebowitz correctly predicted that the music industry would be seriously hurt because it was so cheap and easy to make perfect copies and distribute them. Today he sees similar harm to other industries like publishing and television (and he is serving as a paid adviser to Viacom in its lawsuit seeking damages from Google for allowing Viacom’s videos to be posted on YouTube).

Trying to charge for songs and other digital content is sometimes dismissed as a losing cause because hackers can crack any copy-protection technology. But as Mr. Lanier notes in his book, any lock on a car or a home can be broken, yet few people do so  or condone break-ins.

“An intelligent person feels guilty for downloading music without paying the musician, but they use this free-open-culture ideology to cover it,” Mr. Lanier told me. In the book he disputes the assertion that there’s no harm in copying a digital music file because you haven’t damaged the original file.

“The same thing could be said if you hacked into a bank and just added money to your online account,” he writes. “The problem in each case is not that you stole from a specific person but that you undermined the artificial scarcities that allow the economy to function.”

Mr. Lanier was once an advocate himself for piracy, arguing that his fellow musicians would make up for the lost revenue in other ways. Sure enough, some musicians have done well selling T-shirts and concert tickets, but it is striking how many of the top-grossing acts began in the predigital era, and how much of today’s music is a mash-up of the old.