WSJ writes about the growth as AOL and Electronic Arts join the action:
The fantasy-sports league phenomenon lies at the crossroads of sports, technology and media.
Fantasy leagues have been around for decades, but they were largely a cottage industry in the early years because compiling the statistics required poring over box scores of games for hours each week. Then, the Internet made it easy for online services to keep the statistics centrally and update scores automatically. A companion corps of commentators and data providers has arisen to peddle information and analysis.
Now, there are fantasy leagues for stock-car racing, cricket, pro cycling, and even bass fishing. But football, the most popular U.S. spectator sport, boasts the biggest fantasy following, in part because its relatively short season and one-game-per-week schedule make it easier for players to follow. Over 90% of all fantasy sports players participate in football, compared to just over 60% for baseball, according to the Fantasy Sports Trade Association.