Btw, just to show my views are not some peculiar raving:

"How are all harmful monopolies created?
The sole source of harmful monopolies is the government, which is the only agency that has the power to physically force competitors out of business, i.e., it is the only agency that has the power to outlaw (i.e., regulate) competition. As evidence, witness the United States Post Office, which makes it illegal for anyone to charge less than 34¢ for first class mail (one entrepreneur attempted to compete by charging 5¢ -- he did not get far). Other examples include the East India Company of the 17th and 18th centuries, the American Pacific Railroads of the 19th century, and the AMA's monopoly over the prescription of medicine in the 20th century."
http://www.capitalism.org/faq/monopolies.htm

"Nathaniel Branden responds:
One of the worst fallacies in the field of economics — propagated by Karl Marx and accepted by almost everyone today, including many businessmen — is that the development of monopolies is an inescapable and intrinsic result of the operation of a free, unregulated economy. In fact, the exact opposite is true. It is a free market that makes monopolies impossible. "

http://www.nathanielbranden.net/ess/ton01.html

This was a result of a net search, and were first two I found with a fairly concise description of monopolies.