Americans love a good deal, as evidenced by the spectacular rise of group buying giants Groupon and Living Social. A new report by daily deal aggregator Local Offer Network now offers the numbers: U.S. consumers spent $1.1 billion on daily deals in 2010 and are expected to spend $2.7 billion in 2011 - a 138 percent jump in revenue.

Groupon is the big winner, expected to bring in between $3 billion to $4 billion worldwide in 2011 - up from $760 million last year. TechCrunch estimates the Chicago company will capture 50-75 percent of the U.S. market in 2011. However, Local Offer Network suggests the group-buying momentum will continue and there is still plenty of room for competition, a bit of good news for Seattle daily deal startups like Tippr, DealPop, Yubit and Deal Co-op.

The other good news is that deal sales are accelerating: 40,000 deals were purchased in the first quarter 2011, nearly two-thirds of the 63,000 total deals sold in 2010.

Local Offer Network also predicts that the overall number of competitors will continue to grow in the next year. In the first quarter of 2011, the company has already tracked 117 new deal sites, nearly double the number of entrants a year ago. (Though it says the churn rate - sites that are purchased, fail or go dormant - for these sites is about 25 percent.)

To compile its data, Local Offer Network has tracked 90,000 deals across 322 group-buying sites in the U.S. since January 2010. It found that the Food and Drink and Beauty, Spa and Massage categories were most likely to get consumers to dig out their credit cards, with Fitness and Nutrition, Sports and Recreation, and Home Products and Services trailing behind. It also reports that the biggest cities for daily deals were Chicago, New York City and San Francisco. Seattle tied with Minneapolis and Austin for fifth place in terms of percentage of offers published.

Consumers were big winners, saving an estimated $1.2 billion in 2010 and potentially saving $3 billion in 2011. On the flip side, businesses forfeited $1.76 billion in revenue, according to Local Offer Network, echoing a Rice University study that suggested daily deals are good for consumers, but bad for businesses.