It also has created a major revenue stream for baseball's ownership.
MLB.com, which is run by MLB Advanced Media in New York City, had 1 billion visitors and made $135 million in 2004, said Jim Gallagher, senior vice president for corporate communications for MLBAM.
Among MLB.com's primary features is MLB.TV, a subscription service that allows users to watch the live television broadcasts of games online.
Bob Bowman, chief executive officer of MLBAM, said there are more than 200,000 subscription customers already and he he expects about 400,000 by the end of the season.
MLB.TV offers subscriptions on a daily and monthly basis, as well as prorated subscriptions for the rest of the season. Bowman said monthly and daily are the most popular formats, making up about 40 percent of subscription sales each.
Despite its growing popularity, Bowman said MLB.TV will not negatively impact television ratings for games.
"It's not anyone's first choice" to watch a game on a computer screen, Bowman told United Press International. "A computer monitor isn't as good as a 42-inch flat-screen TV."
Russell Adams of the Sports Business Journal said he does not think Bowman's argument will be good enough for television executives, however.
"TV networks have such a huge investment in the televised product they will fight vigorously to maintain their exclusivity," Adams told UPI.
MLB.TV uses game broadcasts from each home team's local station for every game. Bowman said for some of the few games this year that will not be covered by any television station, MLB.TV will dispatch its own announcing crew for the online broadcast.
MLBAM, which was created in 2000, answers not to Baseball Commissioner Bud Selig's office, but to the owners of the 30 Major League clubs, all of whom own equal shares. Bowman said he answers to a seven-member board of directors made up of seven team owners.
Gallagher declined to comment on the net worth of MLBAM, but Adams said he would place the value at close to $1 billion.
In January, MLBAM struck a five-year, $50 million deal with the MLB Player's Union for exclusive rights, which gives MLBAM more flexibility in offering merchandise and fantasy baseball products, and also puts MLBAM in the position of negotiating deals with sites such as ESPN and Yahoo! for rights to the players.
In recent months, controversy has erupted over what constitutes a broadcast of a baseball game.
MLB and MLBAM claim that a real-time graphic display of game statistics and information should be considered a broadcast and thus be subject to copyright restrictions.
Most major sports Web sites, such as ESPN.com and Yahoo! Sports, offer some real-time game updates.
"It's our belief that it's an exhibition of the game, which makes it a copyright endeavor," Bowman said. "It's no different from audio and video."
Adams disagreed. "Generally, data emanating from games is public domain," he said. "Anyone can take the data and disseminate it any way they want."
Adams suggested MLB make more stringent rules for media credentials. Even then, though, he said, Web-site content providers can watch the games from home and put the information online.
Another feature offered by MLB.com is MLBlogs, a network of baseball-related Web blogs found at MLBlogs.com. The site offers blogs from former players such as Hall of Fame pitcher Tom Seaver and manager Tommy Lasorda, and also sells blog space for fans at $4.95 per month or $49.95 per year.
"Everyone has an opinion in baseball," Bowman said. "Fans enjoy hearing from experts."
Bowman said when MLBAM began charging people money to make an MLBlog, it "hurt our traffic, but raised the quality of the work."
MLB.com also offers electronic ballots for the Baseball All-Star Game, where fan votes determine the starting lineup for the game. Gallagher said in 2004, some 10.6 million ballots were cast online, approximately 40 percent of the total.
Gallagher said he expects online ballots to jump to as much as 50 percent of the total ballots this year. Balloting ends June 30, and paper ballots are provided at all major league stadiums, as they have been for decades.
Bowman said he is not concerned about the possibility of online ballot-stuffing. "I actually encourage it," he said, noting that as a youth he would often cast hundreds of ballots for stars from his hometown Milwaukee Brewers.
"Being able to vote from overseas has changed the whole process," Adams said. He said thanks largely to international online ballots, Japanese player Ichiro Suzuki has been voted to the All-Star team every year he has been eligible.
The National Basketball Association also offers international online balloting for its All-Star Game, and 7 foot 6 inch Chinese player Yao Ming has been the leading vote-getter every year he has been eligible.
Bowman said he has faith in the fans.
"It will be hard to quarrel with the teams that end up getting voted in," he said.
Elliott Smilowitz is an intern for UPI Science News. E-mail: firstname.lastname@example.org