Well if you knew stock movements like the poster suggested, you could achieve huge returns by playing with options. Like the options on Nokia that went from a few pennies to a dollar or so when MS announced the purchase. Options jump around by a huge lot each week. So it seems that starting from $100, if you knew were things were going each week, you'd make a ton of money. (There's a limit as you get more money - it's uh, hard, to double a billion dollars on a limited set of options in a week, versus only $100.)