The big picture: Google purchased Android for around $50 million in 2005, a considerable bargain in hindsight. Android has the largest market share of any mobile operating system by a substantial margin although increased momentum by Google's Fuchsia OS could change that in the coming years.

Even some of the wealthiest and most successful people in the world live with regret. For Microsoft co-founder Bill Gates, it involves Android.

During a recent interview with venture capital firm Village Global, Gates said his greatest mistake ever is whatever mismanagement he engaged in that caused Microsoft not to be what Android is (that being, Android is the standard non-Apple phone platform).

“That was a natural thing for Microsoft to win. It really is winner take all. If you’re there with half as many apps or 90 percent as many apps, you’re on your way to complete doom. There’s room for exactly one non-Apple operating system and what’s that worth? $400 billion that would be transferred from company G [Google] to company M [Microsoft].”

Gates wasn’t too torn up about it, however, noting that despite the colossal mistake, other bets like Windows and Office were still very strong and as a result, they are a leading company. “If we had gotten that one right, we would be the leading company. But oh well.”

As The Verge highlights, it’s a bit surprising to hear Gates admit as much, especially considering most people associate Microsoft’s missed mobile opportunity with Steve Ballmer. If you remember, Ballmer famously laughed off the iPhone as being expensive and not appealing to business customers because it didn’t have a keyboard. Oops.

Ballmer’s biggest regret? Windows Vista. Yep, that certainly qualifies.