For example, Coca-Cola existed for 17 years before Pepsi even came on the scene. That's longer than all but two of the online "monopolies" he referenced (see the "great new monopolies" link). Beyond that Pepsi has been around fighting Coke for dominance for the past 100+ years.
Same with McDonalds (1955) and Anheuser-Busch (1852).
In all these stories the initial company had as much dominance as online companies do now. Pepsi was founded by a guy who wasn't willing to pay Coca-Cola's prices and realized he could produce Pepsi and sell it for half the price of Coke while still making a profit (See "Twice as much for a Nickle")
On the tech companies you're already starting to see erosion in the older monopolies. Windows is starting to see serious losses from increasing Mac sales, Intel has been beating AMD back with a stick and even Google is having to make improvements to keep Bing at bay.
So it will literally be decades before we can know if the author's thesis is even remotely valid