Billionaire hedge fund manager Bill Ackman announced plans to build a modern-day Berkshire Hathaway (BRK.A 1.42%) (BRK.B 1.38%). Although Ackman and his investors would own most of it, it would be available to invest in as a publicly traded company.Ackman has a unique investment style through his Pershing Square hedge fund. Instead of owning dozens of stocks like many other famous investors do, he tends to prefer spreading Pershing's billions among just a few stocks in which he has the highest level of conv ...