As a minor plot point in The Shockwave Rider, John Brunner describes a combination prediction/gambling "game" called Delphi. Loosely based on the Delphic Oracle, the organizers would post questions such as "When will human brain transplants be done?". Players would then decide on an answer and place bets. Delphi was used by shadowy figures in the government to both determine what the population was interested in, and to influence people's thinking.

Spencer F. Katt's Rumor Central, in the the latest eWeek print edition, describes a one-issue Delphi. For a small bet (via PayPal), you can join a pool of playas in predicting when Mike Tyson will bite someone again.

Ain't the Web grand?