You contradict yourself. "Restrained" is tyranny. What you fear happening, fraud and coercion cannot be prevented if they are an integral part of the recipe.
Also the free market isn't necessarily "capitalism" or at least the kind that exists today.
restraint is not tyranny. getting everything you want all the time because youre the birthday boy, is tyranny to everybody else, and turns the child into a monster.
restraint is the heart and soul of the human condition. we plan for the future, and anticipate possible problems, like:
merchant houses attaining so much wealth they can depose kings and popes at a whim and install their own puppets (see the italian city states)
behemoth banks who can squish an entire economy like a bug simply by calling in their markers (see the rothschilds)
corporate megaliths who dominate an entire market and use that power to squeeze out their competitors, pinch their suppliers and ruin smallholders without even working very hard to do it (see walmart)
robber barons who seize control of everything that falls within their grasp and wring every penny out of the people, their employees, and any one else who falls into their Mighty Money Juicing Machine (see the late 19th century)
hordes of fools scrambling fopr an easy buck on leveraged capital investing in foolish bullshit on margin, so any minor hiccup sends the entire financial, capital and market system into freefall (see the great depression)
wise and careful regulation CAN prevent such things, but sadly wisdom is found only among the learned, and the learned are not in politics.
further we were not discussing Current Capitalism which is out of control and needs some restraint, but rather the IDEAL of capitalism. that was a red herring.