As expected, Facebook and Groupon backer Mail.ru, has filed to go public on the London Stock Exchange. There had been talk that the company, which was formerly known as Digital Sky Technologies, was preparing to go public as far back as May 2009 and the company confirmed it would file for an IPO last month saying it was “well positioned to benefit from the expected growth of the Russian internet advertising market and the increase in internet value-added services.” The company says today that it will also use some of the proceeds from the offering to up its stake in Russian social network vKontakte to 32.49 percent from 24.99 percent.