I've long been in favor of ending the Sherman act for this reason. You can target companies that are politically opposed to you by just a bit of rhetoric and government over reach. One interesting way to think about what good breaking up companies do is think of Standard Oil's breakup leading to a butterfly affect so to speak that encouraged the increase usage of carbon base fuels. There were relatively crappy electric car models in the 1900s, there was actually a point where the electric car worked better than gas (1). If Standard Oil was to remain together and lack of competition meant higher oil prices this could have led Ford and others to research ways to make the electric model more capable for the masses as consumer demand would seek such alternatives. 100 years later, we may be in a much better position environmentally..maybe. Just a butterfly effect thought nonetheless. All that said, the best thing to do in order to combat monopolies in the free market is to legalize insider trading and spoofing. The markets will figure it out. Insiders acting on information they know without having to go through SEC hoops would be able to react more quickly and damage firms in ways that could work to destabilize such giants.

1.) https://en.wikipedia.org/wiki/History_of_the_electric_vehicl...