OpenAI CEO Sam Altman, who served as Reddit's chief executive for eight days in 2014, owns Reddit's 8.7% shares, according to Reddit's IPO filing. Altman is the third-largest Reddit shareholder, after Newhouse family's Advance (over 30% ownership) and China's Tencent (over 11% ownership). Reddit is reportedly looking for a $5-billion valuation, which would value Altman's shares at $435 million.