CORP TALK: Various news media sources, including Sacramento Business Journal here and Reuters here, have reported that Russian-based Digital Sky Technologies is increasing its stake in Facebook Inc. with an offer to buy up to US$100 million in employee stock.

With an offer of US$14.77 a share, the Palo Alto-based social networking service’s value now stands at US$6.5 billion. DST currently owns 1.96% in Facebook as of May 2009 with its US$200 million investment.

According to the site, the offer on employee stock is based on a valuation that’s lower than the US$15 billion put on Facebook when Microsoft Corp. first invested US$240 million in the firm in 2007.

According to Facebook chief executive officer Mark Zuckerberg, the DST pricetag brings the value for the service higher than the price originally considered in May 2009.