[Travis]

A friend of mine is part of the team at groupon.com, which is a great group buying site. They've been extremely successful because they've managed to know and target their prime demograpic perfectly. Also, they localize their deals to a city, so that you're buying things like teeth whitening sessions and dinners at fondue restaurants.

But the key to their success has been their customer / market validation, and the singleminded pursuit of their target demographic (which is itself interesting, as they're targeting 25-40 y.o. females in a high socioeconomic class).