Are Groupon users loyal to Groupon, or do they also use other email list coupon sites? I ask because if the answer is "no", I'm not seeing how Groupon can be t

Are Groupon users loyal to Groupon, or do they also use other email list coupon sites? I ask because if the answer is "no", I'm not seeing how Groupon can be that big at all. Google brought something to the table that others could not; Groupon clearly doesn't. Groupon only has on it's competition a small head-start in sales reach. Unless they can some how get exclusivity on small businesses, they aren't doing anything noteworthy not also being done by Living Social or Google or Facebook.