Amy Sussman/Getty Images, John Lamparski/Getty Images When it comes to retirement security, Shark Tank's Kevin O'Leary, Barbara Corcoran and Robert Herjavec have it made, amassing multiples of the $1.46 million nest egg many Americans believe they need to retire comfortably. According to The Street, real-estate maven Corcoran, 77, is worth an estimated $100 million. O'Leary, 72, who became a millionaire when he sold his software company Softkey to Mattel for $4.2 billion in 1999, is worth $400 million. ...