Quote from futures_shark:
There has never been a truly capitalist society, so you can't say that it creates monopolies & oligopolies. Those are usually the result of government involvment, such as laws that restrict competition and "protect" industries.
I actually disagree with this point. I think any industry with economies of scale will tend towards one or a few competitors. As this trend evinces itself, these competitors will use the political system to create additional barriers to any other entrants. It's a chicken and egg question but I think this one has an answer -- and its not the government.
Here is a link to some Stanford case studies that you might find interesting reading.
http://cse.stanford.edu/class/cs201/projects-95-96/corporate-monopolies/development.html