"The reason is crystal clear," said RJ Bell, who runs the sports-handicapping website pregame.com. "It's the social connection. In the NFL, the conference championship games are pretty important, but not many people have parties to watch them. But everyone is going to a Super Bowl party on Sunday. Whether it's taking a chance on a Super Bowl scoring box at a party or on a pool at work, you don't want to be left out."
Wagering on the Super Bowl and the odds that drive it spice conversations leading to the game, and this year the betting story line was especially intriguing.
In Nevada, where only 1 percent of that $10 billion will be wagered, Seattle was cast as an immediate two-point favorite by the most influential casino bookmakers just moments after the Seahawks dispatched San Francisco in the NFC title game.
But the wagering public immediately stormed the betting counters taking the Broncos. In less than an hour, even quicker according to some accounts, the point spread had flipped.
The next morning, Denver was widely set as a 21/2-point favorite.
"A lot of it was about Peyton Manning," said South Point Casino sports book director Jimmy Vaccaro, a Las Vegas veteran. "That was public money going after Manning."
So-called public money refers to wagers made by recreational gamblers.
Sharp money represents bets made by gambling pros.
Normally, early line shifts are caused by sharp money as casino bookmakers respond to informed opinions.
No so this time.
"Super Bowl betting is 90 percent recreational, and those bettors are influenced by brands," handicapper Bell said. "Manning is the biggest individual brand in football."
Jay Kornegay, the longtime director of the popular LVH Casino SuperBook in Vegas, was the one who made Seattle the early favorite.
"In the playoff games leading up to that, the Broncos had not been particularly popular. They were the favorites, but people were on the Chargers and the Patriots," Kornegay said, referring to Denver's opponents in the divisional and conference rounds. "There was all the talk about how Manning didn't play that well in the playoffs."
However, the betting public often reacts to what it has seen most recently, Kornegay pointed out, and apparently Manning's 400-yard passing performance against New England in the AFC championship game made a big impression.
At midweek, both at brick-and-mortar casinos in Vegas and on offshore bookmaking websites, between 70 percent and 75 percent of Super Bowl bets against the point spread were on Denver.
"I still think that there's Seattle money waiting in the weeds," Kornegay said, "just waiting to see if the line goes up."
Kornegay is also known for having popularized Super Bowl prop bets, and this year the list is as long as ever, offering hundreds of bets from the mundane to the exotic.
In the last decade or so, prop bets have grown to represent from 40 percent to 50 percent of Super Bowl betting tickets in Vegas.
Some of the best odds are on the most ho-hum of wagers.
If a bettor wants to bet on heads or tails on the coin flip, the price is minus-103. That means to win $100, the bettor risks just $103. That 3 percent commission is one of the lowest that sports bettors will pay. Usually, it's around 10 percent.
Some prop bets mix sports, such as pitting the number of birdies Tiger Woods will make in the fourth round of the Dubai Desert Classic on Sunday against receptions by Denver wide receiver Demaryius Thomas.
"I like prop bets where there's some real thinking outside the box," said handicapper Micah Roberts of the Linemakers on the Sporting News website. "I've seen some that have you betting the past and the future. One has Manning's total passing yardage against John Elway in his last Super Bowl, minus some yardage for Elway."
Prop bets have done more than just increase Super Bowl wagering for the casinos. They've become an important part of the buzz that drive even casual fans to Vegas, said casino bookmaker Vaccaro.
A typical recreational bettor in Vegas will have a wager on the game and seven to eight prop bets, Vaccaro said, and that gives a fan a personal rooting interest on almost every snap.