And while Groupon argues it will be sustainable once it hits a certain threshold, its business is actually decaying in older markets like Boston - http://www.b

And while Groupon argues it will be sustainable once it hits a certain threshold, its business is actually decaying in older markets like Boston - http://www.betabeat.com/2011/06/03/groupons-business-is-decaying-in-its-established-markets/ http://www.betabeat.com/2011/06/03/groupons-business-is-deca...