To assign a value of $6 BN to a coupon idea is ludicrous. Anyone can replicate the process.
The Groupon guy was doing the greed squad a favor by not selling his pile of nothing.
well, anybody can set up a webshop (but only amazon got a dominant position), or some social network site where you can update your status etc (but only fb got dominant position).
Some companies will end up in dominant position, even though it looks easy for everybody. Brand recognition, and being early may be enough.