their success is limited by how much money they can move. When you are moving that kind of money through quant strats you start to move the market. It's easy to capture a triangle arb with 20k, almost impossible to do it with 10B, because by the time you enter and exit the trade the arb no longer exists or you were moving the market against yourself with your own trades.

One of the genious thing that rentech did was long out of the money bonds, and short newly issued bonds. Seems like such a simple strat, but when you crank up the leverage you can make alot of money.