If your company's dominated by one type of person, you run the risk of tunnel vision. You might move fast — but you'll often drive straight into traps as you grow. Truly scalable companies need a diverse portfolio of viewpoints to see the opportunities others miss. Sallie Krawcheck knows this well.She rose through the ranks of Wall Street and saw firsthand the challenges a lack of diversity brings. After serving as CEO of Sanford Bernstein, Smith Barney, Citi's Wealth Management and Merrill Lynch Wealth Management, Sallie went on to found Ellevest, an investment platform aimed at women. Her straight talk — and hilarious asides — create the clear business case for diversity of all kinds. Cameo appearance: Steven Johnson (host of the podcast American Innovations; and author of best-selling books, including the recent "Farsighted: How We Make the Decisions That Matter the Most").