According to a recent SEC filing by group-coupon site Groupon, the company has already raised $500 million out of an ongoing $1 billion fund-raising round thanks to participation from several investors, including Russian venture capital firm Digital Sky Technologies. The information was derived from a Securities and Exchange Commission form D Notice of Exempt Offering of Securities which was filed by the company on Dec. 30.

   Other firms reported to have participated in this fundraising round include Fidelity and Morgan Stanley. According to unnamed sources cited by a variety of tech blogs and sites, including TechCrunch and paidContent, much of the funds are intended to be used to buy back equity from the company's founders and other executives.