>>11953527
Early on in the game it is in your interest to buy as much stock in everyone's railroads as you can before it's all snatched up. You can, and probably should, take margin loans to do this.
But if EVERYONE is doing that, and there's a hiccup in the economy or your company, share prices will fall, and if you're heavily leveraged you'll face a margin call and need to sell something.
In which case your best bet is to sell your holdings in other people's companies, which will depress those prices, and then THEY'LL face margin calls, etc... It's a downward spiral that can leave everybody bankrupt.