I think a ferengi megacorp is impossibel unless the workers are from offworld. Ferengi lack the discipline to keep a megacorp together.
Through my (possibly limited) understanding of free market of pure capitalism, corporations are not really part of the free market system. Instead of people competing to get their share of the pie, a corporation pools the resources of many to get the whole pie before anyone else gets the chance.
Corporations also lobby for rules to keep their competition out.