BOSTON – Whether gamblers placed their money on the St. Louis Rams or the Tennessee Titans, growing numbers of them made their wagers online.

Cyberspace wagering on Sunday’s Super Bowl was expected to more than double this year, compared to last, to as much as $50 million, said Jonathan Ader, who monitors the gaming industry for Bear, Stearns & Co.

That’s a pittance compared to the total amount of legal and illegal bets on Sunday’s contest, which is predicted to come in at between $50 billion and $100 billion.

The number of companies offering Internet betting sites has tripled in the past year from about 30 to close to 100. According to Frost & Sullivan, a marketing consulting firm, these new ventures will gather an estimated $640 million from sports wagers this year in an industry that began only five years.

Super Bowl Sunday “is absolutely our biggest day of the year,” said Mike Edwards, a spokesman for Betmaker.com, a Costa Rica-based online casino.

But the growing popularity of placing online bets is bringing together opponents with widely differing agendas, from casino lobbyists to gambling opponents, the NFL, politicians and credit card companies who are worried about the unregulated nature of the industry.

“As a professor at Harvard said, this is the crack cocaine of gambling,” said Sen. John Kyl, R-Ariz., a vocal critic of online sports gambling.

Kyl has sponsored legislation that would outlaw Internet betting and wants to force Internet service providers to terminate services to online casinos and bookmakers.

Sports gambling in the United States is legal only in Nevada,

“The fact is, sportsbooks are a minimal part of the Nevada bottom line on Super Bowl weekend,” said Frank Fahrenkopf, president and CEO of the American Gaming Association, which represents U.S. casinos. “We do think that it’s imperative that gambling is appropriately regulated to maintain its integrity, and with the Internet we just don’t think that’s possible.”

Most of the virtual gaming industry operates out of places such as Curacao, Costa Rica and Antigua, which are beyond the reach of U.S. government regulators.

Easy access to online gambling makes it a dangerous industry, said Kevin O’Neill of the Council on Compulsive Gambling of New Jersey.

“For people who are not part of the underworld or the mob, they just go on line and in five minutes, they’re up and running,” O’Neill said. “So the upshot is that more and more young people will have access to sports gambling that never would have had it before.”

Credit card companies object to the online gaming industry because it isn’t regulated.

American Express and Discover Financial Services, which offer the Discover card, explicitly forbid customers from using their cards for online wagers because of the unregulated nature of the industry. Mastercard International and Visa USA recently began using a coding system allowing financial institutions that issue credit cards to decide whether to authorize bets.

Despite this opposition, officials with online casinos still expected a large draw for the Super Bowl. Betmaker.com expected about 25,000 gamblers alone, Edwards said.