There are cases of monopolies that are the result of a single competitor being so efficient, cost attractive and capable of serving its market that it becomes a "natural monopoly" for whatever period it can sustain that. It's the one type of monopoly that isn't viewed dourly because it tends to represent the best possible result for both sides of the equation.

Standard Oil's monopoly, and its inability to maintain it (and why), is described by David Friedman in the Machinery of Freedom. While I can't really do the response real credit here, the simple answer is that it works quite the opposite to what you imply -- without government intervention, Standard Oil couldn't keep competition from breaking their hold. But with intervention, monopolies are more easily captured and maintained.

You can find some of Freidman's answer here (PDF, see the end of page 21 and a few beyond as well as other parts that speak to Standard Oil and more specifically to Rockefeller's unsuccessful strategies.) In all, it's an EXCELLENT read if you're really interested in how free markets topple rather than uphold monopolies and oligopolies.