Think of your favorite old TV show. Chances are, you can point to a time when it just seemed to go downhill. Barney Fife left Mayberry. Lucy and Ricky moved to the suburbs. Col. Blake's plane went down. Scooby Doo was joined by Scrappy. The "Very Special Episode." All of these, according to Jon Hein, are examples of "jumping the shark."

Hein coined the phrase from an episode of Happy Days in which Fonzie, on water skis, jumped over a shark. That point signaled the beginning of Happy Days' creative decline.

Hein built on the concept in 1997 with a website (http://www.jumptheshark.com) that analyzed 200 TV shows based on "votes" from friends. Today, the site boasts millions of votes on over 2,000 television programs, and even the networks follow the site to gauge the popularity of their shows.

In his book, Jump the Shark: When Good Things Go Bad (Dutton, 2002), Hein moves beyond TV and applies his biting analysis to music, sports, politics and celebrities. "We all know that there's a moment," ...