The group buying industry has sprung out of nowhere over the past two years. A new report (embedded below) by daily deal aggregator Local Offer Network puts the U.S. gross revenues across the industry at $1.1 billion last year, and estimates gross revenues will grow 138 percent to $2.7 billion in 2011. Groupon alone, according to other sources, is expected to bring in between $3 billion and $4 billion this year, up from $760 million las year, but those numbers are worldwide. If you figure at least half of Groupon's revenues come from the U.S., you can get a sense of how much it dominates the market—capturing anywhere from about 50 to 75 percent of expected industry revenues this year.