According to Douglas Knight, commenting on this blog entry,
if the mere existence of a barrier to entry means that there is a monopoly then every single business in the U.S. is monopoly.
That’s actually a good way of looking at things. Everything has partial monopoly power. It’s the only way to make money. The interesting question is how the barriers differ from industry to industry. Also, this perspective discourages people from getting hysterical about monopolies.