Your concerns are only natural, and not unwarranted, but in real life one finds that monopolies can become oppressive only when competition is somehow forced out of the picture, usually by regulations, licensing requirements, or other government interference.

Natural monopolies, where a large company holds a commanding position without the use of force, are rare but not impossible. Alcoa Aluminum was one such. Microsoft could almost be considered such, although they tend to fall off the "no force" wagon.

Massive investments do not prevent competition. New businesses dump billions into investments all the time. Try pricing out a microchip factory sometimes.

The competition can be more complicated than it appears, and when a monopoly becomes lethargic or abusive, can slip in even when theoretically prevented by these regulations. The best current example is the Post Office, which once held an exclusive government license to transport first class mail. It was a crime to compete with them. What happened was not that someone else started delivering letters, but that new ideas came out of the woodwork like fax machines and e-mail.

Competition for a power company may not be another power company with duplicate feeders, although this is certainly possible, but maybe a company that develops a fuel cell that burns the natural gas delivered to most homes, or a cheap solar panel array. A power company that started charging ruinous prices for its product would make such competition very attractive to customers. Power companies have, of course, taken a dim view of some of these things. It took a major overhaul of some laws in California to set up a protocol where homeowners could link their own power supplies into the grid, and actually sell power back to the system.

Another good example is cable television. It was typical in the past for a town to assign a certain cable company an exclusive license for that area, shutting out other cable companies. As you know, this led to almost legendary bad service, and high prices. Then the dish networks came along, ignoring the cable lines altogether. Suddenly in my town we had a ball game again.

For high speed internet I have a choice of phone lines, cable, or dish, all fighting for my money. None physically get in each other's way, although some years back no one could have anticipated that anyone would have an alternative to the phone company.

Getting back to Microsoft: most people view this as the ultimate Robber Baron company, beyond all competition.

Not true. Open source software is making a considerable dent in Microsoft's "monopoly." Unfortunately, they appear to be resorting to using government force to make their competition illegal, which you can easily do in a mixed economy. I hope it doesn't work. One article on this controversy can be found here. This is not a major focus of interest for me, not being a computer whiz, but the point is that the free market is nipping at the heels of even the mighty Bill Gates. We'll see what happens.

Every tree, deer, and length of road is owned by someone. Usually the government. This seems to bother very few people, despite the fact that our government, thanks to our mixed economy principles, is becoming largely run by the rich folks that make you so paranoid in the first place.

I'll tell you one other thing, if the public forests and grazing lands were all privately owned, the lumber companies, mining companies, and ranchers wouldn't be getting the use of them for the rock-bottom subsidized prices they pay now, which encourages overuse of resources.