Many people knew Apple chief executive Tim Cook was gay. Since 2011, he has topped Out magazine's Power List, and he has made no effort to get off it. Still, his "proud to be gay" column in Bloomberg BusinessWeek is an important and courageous act — not least because it gives rise to new questions about Apple's diversity issues.

Strange as it may seem in 2014, Cook is the first chief executive of a Fortune 500 company to come out in public. Members of this exclusive club are still unsure whether that's wise, and just a few years ago, it wasn't. In 2007, John Browne resigned as chief executive of BP after being outed by a British tabloid. He has since written a book about being a closeted gay in big business.

"To a headhunter I would have been seen as 'controversial,' too hot to handle," Browne wrote. "Sadly, there were some people, mostly from the business world, who never again displayed any warmth to me."