Techcrunch has confirmed it.
http://techcrunch.com/2013/01/25/rabois-left-square-over-sex...
http://techcrunch.com/2013/01/25/rabois-left-square-over-sex...
It could be legit, but the bar should be higher than this.
http://allthingsd.com/20130125/keith-rabois-long-statement-o...
[edit to add the question]