Near the peak of her company's success, Martha Stewart inadvertently summed up both the strength and the vulnerability of the empire she had built. At an advertising-industry conference in Detroit in 2001, she was speaking to a crowd of starstruck ad executives when somewhere in the crowd, a voice piped up with a fawning question. "Someone asked her, 'You dispense all this advice. Who taught you all these things? Who's your mentor?'" recalls Samir Husni, a magazine consultant who also spoke at the meeting. "She said, 'Me. Me. I did it all by myself.'"
That unyielding self-reliance helped build Martha Stewart...