You raise an interesting topic. I like to think that I support free market capitalism in all its glory; the less government involvement, the better. However, this understanding presupposes fair competition. With the rise of the tech titans, we have seen companies that have a level of control unseen in the great industrial monopolies of the Gilded Age. Today, we have companies that control vast amounts of information which has given them insights unlike the world has ever seen. John D. Rockefeller may have cornered the oil market, but he was never able to eavesdrop on private conversations of customers as a means of trying to increase sales as companies can today. If you wanted steel you would have to go through Andrew Carnegie, but he would not have been able to peer into the private communications of millions of American citizens.
The sheer power that tech companies have today separates them from their corporate ancestors, and it also makes them much more dangerous than ever before. At some point, citizens will need to stop and ask where these companies are headed in the future. How much of our lives will they be involved in? Will we have any privacy left?
Add to this the interesting development which hasn't really been discussed but which really raised its ugly head during the gay marriage debate: corporations taking public stances in favor of a specific hot-button social issue. I think that the gay lobby inside companies was strong and resistance was weak which led to this kind of unprecedented maneuver. What if corporations decided to go even further and force consumers to accepting specific values as a condition of doing business? Could Amazon include a message on its checkout page which stated "as a condition of concluding this sale, you agree to have an automatic message sent to your representative to urge him to defend abortion on demand"? Could Apple agree to sell iPhones only to those who are registered Democrats?
This is only the tip of the iceberg, though. It's easy to see how they could use their hegemony to push a certain socio-political vision in our country, whether we - the citizens - agree with it or not. That's a very scary thought.
A lot of sci-fi or dystopian storylines of the future frame power struggles as involving one or more corporations. I can see why this is.