They don't go long and take a chance on the price sky rocketing. They just play the order flow and clip a few bucks off of each trade. Look at Goldman Sachs they make a 10th of a penny per trade but make millions and millions off those computerized trading programs they run.
Market Makers don't investigate or complete any due diligence on these companies. They just make sure there is a liquid market and make their money off of each trade completed.
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