Ask HN: How are monopolies lost?

Speaking about Apple's fall in the 90s, Steve Jobs says: "Apple had a monopoly on the graphical user interface for almost 10 years. That's a long time." [1]

Then he asks: "And how are monopolies lost?", following with his explanation for the phenomenon, which I don't think is accurate, because he bases it on the supposition that monopolies are created by great products, which certainly has not been the case with Windows.

I read somewhere that monopolies are not lost: they become irrelevant. Although I don't know if that is correct either: at Apple's case, what made it loose its monopoly was not technological irrelevancy, but the commoditization of complements promoted by Microsoft[2], which offered a slower, uglier, less robust, but cheaper alternative for the masses, forging the base for the Windows platform that would create a vicious circle, "forcing" users and developers to use its graphical interface.

But I don't have much knowledge about the rise and fall of monopolists, and that's why I would like to hear your answers, besides the obvious answer of governmental intervention.

Do you agree with my theory about Apple's fall? And more generally, what other cases do you know of monopolies that were not lost by technological irrelevancy or intervention?

[1] http://www.businessweek.com/print/bwdaily/dnflash/oct2004/nf20041012_4018_db083.htm?chan=gl

[2] http://www.joelonsoftware.com/articles/StrategyLetterV.html