This summer, the two big domain sales came through an auction held by Moniker.
Data.com was reportedly sold for $4.5 million, and Social.com was reportedly sold for $2.6 million. Shortly thereafter, it was pretty simple to notice that Data.com had been acquired for a rebranded marketing channel for their recent acquisition of Jigsaw.
So the question remained, why Social.com? Perhaps not too hard to determine, given their recent acquistions in the social enterprise space... consider a quote from their recent PR regarding the acquisition of Assistly in September:
"Salesforce.com is leading the shift to the social enterprise, helping companies leverage social, mobile and open cloud technologies to put customers at the heart of their business. For many organizations, that shift begins with customer service, as businesses engage with their customers where they are now – on social networks like Facebook and Twitter."