David Rubenstein is a kingpin in the world of private equity as a co-founder of The Carlyle Group. Rubenstein is significantly involved with the Harvard Business School and during one of his remarks at the school he compared private equity to sex to describe the buyout bubble.
Still, Rubenstein is a very careful investor and even so has made a few decisions that he regrets. A very important deal that he missed was to be one of the first investors in the social networking giant Facebook. Rubenstein's now son-in-law was a classmate of Mark Zuckerberg at the Philips Exeter Academy.