April 2010: Groupon valued in the $1.35b range: http://techcrunch.com/2010/04/18/its-official-groupon-announ...
January 2011: Groupon values itself in the $15b range with an IPO: http://dealbook.nytimes.com/2011/01/13/groupon-readies-for-a...
Hmmmmm....