With all investments there is a chance that they could lose ALL the investment; if the company goes bust, generally banks will allow you to choose whether you'd like Low, Medium or High Risk investments, the riskier the trade, the more money could be gained

I just watch the movie "Attack on Wall Street". In it a banker loses his friends money. The guy wants to take out his money to pay for his wife's operation but his banker friend has lost all of it.

Can someone shortly summarize this process for me. How it's possible? I got to a friend who is an investment banker and I give him my pension, savings and so on... how can he lose it ALL due to bad investing? What, he just invests in companies that go bust and all the money is done? Can such bad investments happen fast, can the market turn that fast upside down on some deals?

Are there any documented cases of investment bankers losing other peoples money due to bad investments or negligence. NOT due to scheming! Losing money without malicious intent but due to negligence, miscalculations and so on.

If not could someone give me a hypothetical example on how an investment banker can lose other people's money due to his own mistake.

Thank you.