Did so just last week, and I just purchased my first groupon (apparently, in Groupon vernacular, 'groupon' is both a noun to both explain and brand their particular type of coupon as well as a pronoun).
For $25, I bought $50 worth of sushi at a Seattle sushi restaurant that sounds nicely above average. A no-brainer as I'm down that way often, and Sushi's my favorite dine-out meal.
Interesting phenomenon. When I started to make my purchase at around 7 this morning, they'd sold 150 of this particular coupon. By the time I concluded my purchase, that number was up to 175. Apparently an initial hurdle of 250 sales had to be satisfied to make it a viable offer and before they would send me the link to print my coupon which can be used as early as tomorrow and is good through July. By the time they sent me that confirmation half an hour ago, 1600 had been sold. A cap has been set at 2500 and obviously they'll have no problem reaching that.
But look at what that means to the restaurant. They're giving away $62,500 worth of profit in order to capture the attention of 2500 potential new customers--and their friends. If they're a new business this could set them for life. Word of mouth doesn't travel an inth that fast. The question begs: should I wait to use this as they'll be slammed for the next few months, or should I use it immediately before quality goes downhill?