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Will fans on the sidelines violate the NFL's rules?

U.S. prosecutors have recently shut down a group of websites that planned to live-stream the NFL's moneymaking Super Bowl. But there’s little prosecutors can do to stop the real problem in the stands: smartphones.

Ten websites that provided links for pirated streams of games in the National Football and Hockey Leagues, the National Basketball Association, World Wrestling Entertainment and Ultimate Fighting Championship were seized by prosecutors early Tuesday, to prevent illegal video streams that cut into revenues. But if fans can use smartphones to stream Sunday’s golden goose -- and they most assuredly can -- the NFL may still have a problem on its hands.

"We greatly appreciate the efforts, time and resources that the federal government, including Homeland Security Investigations and the U.S. Attorney’s Office, has dedicated to the problem of online piracy,” NFL spokesman Dan Masonson told FoxNews.com.

While declining to address the issue of smart devices in the stands, the NFL instead backed itself by actions led by prosecutors.

“[We] believe the current action sends an important message to those who illegally pirate the content of others," Masonson said.

The illegal sites seized were atdehe.net, channelsurfing.net, firstrow.net, hq-streams.com, hq-streams.net, ilemi.com, iilemi.com, iilemii.com and Spanish sites rojadirecta.com and rojadirecta.org. Sports leagues have taken a huge blow financially from these illegal sites, with prosecutors estimating annual damages in the millions.

Major League Baseball, which has been widely recognized for its efforts to use digital technologies to distribute its content, declined to comment on concerns about smartphone video clips from the 2010 World Series.

But all leagues are quick to guard their most precious asset: video images of the big games. Results of major money loss are seen when leagues and broadcasters “are forced to pass their losses off to fans by raising prices for tickets and pay-per-view events,” U.S. Attorney for the Southern District of New York Preet Bharara said in a statement following the website seizures.

“With the Super Bowl just days away, the seizures of these infringing websites reaffirm our commitment to working with our law enforcement partners to protect copyrighted material and put the people who steal it out of business.”

Prosecutors are working to get the illegal sites to forfeit their domain names, and visitors to such sites will notice banners indicating their seizure by Homeland Security.