How hard would it be to go a week without Google? Or, to up the ante, without Facebook, Amazon, Skype, Twitter, Apple, eBay and Google? It wouldn’t be impossible, but for even a moderate Internet user, it would be a real pain. Forgoing Google and Amazon is just inconvenient; forgoing Facebook or Twitter means giving up whole categories of activity. For most of us, avoiding the Internet’s dominant firms would be a lot harder than bypassing Starbucks, Wal-Mart or other companies that dominate some corner of what was once called the real world.

The Internet has long been held up as a model for what the free market is supposed to look like—competition in its purest form. So why does it look increasingly like a Monopoly board? Most of the major sectors today are controlled by one dominant company or an oligopoly. Google “owns” search; Facebook, social networking; eBay rules auctions; Apple dominates online content delivery; Amazon, retail; and so on.

There are digital Kashmirs, disputed territories that remain anyone’s game, like digital publishing.

But the dominions of major firms have enjoyed surprisingly secure borders over the last five years, their core markets secure. Microsoft’s Bing, launched last year by a giant with $40 billion in cash on hand, has captured a mere 3.25% of query volume (Google retains 83%).

Still, no one expects Google Buzz to seriously encroach on Facebook’s market, or, for that matter, Skype to take over from Twitter. Though the border incursions do keep dominant firms on their toes, they have largely foundered as business ventures.

The rise of the app (a dedicated program that runs on a mobile device or Facebook) may seem to challenge the neat sorting of functions among a handful of firms, but even this development is part of the larger trend. To stay alive, all apps must secure a place on a monopolist’s platform, thus strengthening the monopolist’s market dominance.

But it’s hard to avoid the conclusion that we are living in an age of large information monopolies.

Could it be that the free market on the Internet actually tends toward monopolies? Could it even be that demand, of all things, is actually winnowing the online free market—that Americans, so diverse and individualistic, actually love these monopolies?

The history of American information firms suggests that the answer to both questions is “yes.” Over the long haul, competition has been the exception, monopoly the rule. Apart from brief periods of openness created by new inventions or antitrust breakups, every medium, starting with the telegraph, has eventually proved to be a case study in monopoly. In fact, many of those firms are still around, if not quite as powerful as they once were, including AT&T, Paramount and NBC.

Internet industries develop pretty much like any other industry that depends on a network: A single firm can dominate the market if the product becomes more valuable to each user as the number of users rises. Such networks have a natural tendency to grow, and that growth leads to dominance. That was the key to Western Union’s telegraph monopoly in the 19th century and to the telephone monopoly of its successor, AT&T. The Bell lines simply reached more people than anyone else’s, so ever more customers came to depend on them in a feedback loop of expanding market share. The more customers they reached, the more impervious the firm became to challengers.

Still, in a land where at least two mega-colas and two brands of diaper can duke it out indefinitely, why are there so many single-firm information markets?

The explanation would seem to lie in the famous American preference for convenience. With networks, size brings convenience.

Consider that, in the late 1990s, there were many competing search engines, like Lycos, AltaVista and Bigfoot. In the 2000s, there were many social networking sites, including Friendster. It was we, collectively, who made Google and Facebook dominant. The biggest sites were faster, better and easier to use than their competitors, and the benefits only grew as more users signed on. But all of those individually rational decisions to sign on to the same sites yielded a result that no one desires in principle—a world with fewer options.

Every time we follow the leader for ostensibly good reasons, the consequence is a narrowing of our choices. This is an important principle of information economics: Market power is rarely seized so much as it is surrendered up, and that surrender is born less of a deliberate decision than of going with the flow.

We wouldn’t fret over monopoly so much if it came with a term limit. If Facebook’s rule over social networking were somehow restricted to, say, 10 years—or better, ended the moment the firm lost its technical superiority—the very idea of monopoly might seem almost wholesome.

The problem is that dominant firms are like congressional incumbents and African dictators: They rarely give up even when they are clearly past their prime. Facing decline, they do everything possible to stay in power. And that’s when the rest of us suffer.

AT&T’s near-absolute dominion over the telephone lasted from about 1914 until the 1984 breakup, all the while delaying the advent of lower prices and innovative technologies that new entrants would eventually bring. The Hollywood studios took effective control of American film in the 1930s, and even now, weakened versions of them remain in charge. Information monopolies can have very long half-lives.

Declining information monopolists often find a lifeline of last resort in the form of Uncle Sam. The government has conferred its blessing on monopolies in information industries with unusual frequency. Sometimes this protection has yielded reciprocal benefits, with the owner of an information network offering the state something valuable in return, like warrantless wiretaps.

Essential to NBC, CBS and ABC’s long domination of broadcasting was the government’s protection of them first from FM radio (the networks were stuck on AM) and later from the cable TV industry, which it suppressed for decades. Today, Verizon and AT&T’s dominance of wireless phone service can be credited in part to de facto assistance from the U.S., and consequently their niche is probably the safest in the entire industry. Monopolies may be a natural development, but the most enduring ones are usually state-sponsored. All the more so since no one has ever conceived a better way of scotching competitors than to make them comply with complex federal regulation.

Info-monopolies tend to be good-to-great in the short term and bad-to-terrible in the long term. For a time, firms deliver great conveniences, powerful efficiencies and dazzling innovations. That’s why a young monopoly is often linked to a medium’s golden age. Today, a single search engine has made virtually everyone’s life simpler and easier, just as a single phone network did 100 years ago. Monopolies also generate enormous profits that can be reinvested into expansion, research and even public projects: AT&T wired America and invented the transistor; Google is scanning the world’s libraries.

The downside shows up later, as the monopolist ages and the will to innovate is replaced by mere will to power. In the 1930s, AT&T took the strangely Luddite measure of suppressing its own invention of magnetic recording, for fear it would deter use of the telephone. The costs of the monopoly are mostly borne by entrepreneurs and innovators. Over the long run, the consequences afflict the public in more subtle ways, as what were once highly dynamic parts of the economy begin to stagnate.

These negative effects are why people like Theodore Roosevelt, Louis Brandeis and Thurman Arnold regarded monopoly as an evil to be destroyed by the federal courts. They took a rather literal reading of the Sherman Act, which states, “Every person who shall monopolize…shall be deemed guilty of a felony.” But today we don’t have the heart to euthanize a healthy firm like Facebook just because it’s huge and happens to know more about us than the IRS.

The Internet is still relatively young, and we remain in the golden age of these monopolists. We can also take comfort from the fact that most of the Internet’s giants profess an awareness of their awesome powers and some sense of attendant duty to the public. Perhaps if we’re vigilant, we can prolong the benign phase of their rule. But let’s not pretend that we live in anything but an age of monopolies.