>>Economists, normally, analyse a market from the point of view of the "public interest". With this perspective in mind, self-perpetuating monopolies are almost always a bad thing (unless you believe in such things as centralized planning and dictatorships).

Yes. The full saying is, "competition is good... for the customer." It almost always results in reduced prices and better service. It's obviously never good for businesses, since they have to work harder to win and retain customers.