Jesse Drucker

In the fall of 2010, the Russian billionaire investor Yuri Milner took the stage for a Q. and A. at a technology conference in San Francisco. Milner, whose holdings have included major stakes in Facebook and Twitter, is known for expounding on everything from the future of social media to the frontiers of space travel. But when someone asked a question that had swirled around his Silicon Valley ascent — Who were his investors? — he did not answer, turning repeatedly to the moderator with a look of incomprehension.