Will Groupon last?

I confess, I don't understand Groupon. I mean, I understand how it works. But I don't understand how people will use Groupons much more than regular coupons. I don't understand why Groupon is worth so much, while competing sites that do the same thing are not. And in many cases, I don't understand why businesses sign up for it.

Consider this case, from Posies Cafe:
"Groupon in Retrospect"
http://posiescafe.com/wp/?p=316

This doesn't mean that Groupon is bad. I just think it will be interesting to see how this business model plays out over the years. I wonder if in a few years we'll be looking back and saying "remember Groupon?" and reminiscing about this crazy fad.