"The accident of my success comes from injecting creativity into normal, sterile situations," says Andrew Mason. Like clipping coupons. With Groupon, Mason married consumers' penchant for sales with the business leverage of collective buying to score ridiculously good deals on everything from frozen yogurt to French bistros to teeth whitening. Six million subscribers are offered a new deal on the Web site each day: If a minimum number take the bargain, the coupon is unlocked; if not, it's gone for good. To foster an insider vibe, the 29-year-old Pittsburgh native and Chicago resident favors local spots over national chains and uses humor writers to describe the daily deals. Launched in November 2008, Mason's fresh take on bargain hunting was recently valued at $1.35 billion.