Perhaps you could illustrate your concerns with examples of existing monopolies.
Who needs a monopoly when you have a Cartel? Who needs a cartel when you can afford to buy judges and politicians? Need you look any further than speculator hedge fund managers who engineered (intentionally or not, it almost doesn't matter, and will probably vary from entity to entity) the current crisis. These are the same people who sit on trillions, can influence entire industries through stock and bond sales and purchases, who gamble and bet using seemingly non-existant but entirely consequential instruments called 'derivatives' evaluated beyond the total price of the entire planet several times over (i.e., recognizably unsustainable) that are now funding the campaigns of all these (mostly but not entirely) right-wing governors, senators, representatives, and (if differently) judges in order keep themselves off the hot-seat as the consequences of their actions melt down while going after the middle and working classes to make up the difference (re: wisconsin, ohio, pennsylvania, florida, california, oregon, maine, new hampshire, (the list goes on, and not just in this country, either, if all the protests in europe are of any indication.))
Regardless of how many names there are, there are only 7 actual health insurers in the country, and they operate in tandem more often than in competition with one another, and commit recission with relatively impunity. Interstate exchange laws in regards to credit cards (and, if they get their way, insurers) allow the one state in the nation with the least regulations to allow all the creditors to have their way with EVERY state regardless of local laws; they certainly aren't behaving particularly competitive.
What of military contractors who fail to deliver on contracts on time (and sometimes not at all) in excess of 80% of the time, and well over budget even more often than that? The worker isn't being asked if they approve of that, and no-bid contracts are proliferating. Competition isn't healthy in that realm either.
Taxpayers aren't being asked if they're okay with handing GE and Exxon welfare checks (in the form of unpaid tax refunds (they each having paid in a grand total of 0) and ridiculous subsidies) in spite of both being far better off than self-sustainably profitable. Where's the competition in that?
In the Citizens United case last year, the right-wing supreme court compounded an error they made (in a much earlier case in which they said it was okay for a corporation/business to lie) by saying that these same entities can dispense ~any~ amount of money they want in regards to political advertising (which should not be confused with giving politicans money directly.) Any of the above names can afford to drop five times what Obama raised in advertising and are not required to be honest in the messages they dispense to a public that only has access to corporate owned mass media these days (since these same powers have been systematically getting public media defunded and destroyed.) Is this competitive? Media is a grand monopoly and 90 plus percent of all small radio states that remain are still conservative (quote-unquote) in nature, sometimes in the guise of being a religious station (and thus taking tax money and not having to pay any in) in spite of the majority of their programming being anything but religious.
Instead of paying the price for their shinanigans, these people are using the vast sums of money they've made and continue to make in order to obfuscate the data and buy any and all legislation they can in order to further their interests. Walker talks to who he believed was a Koch, happily going on about his crusade against organized labor. Children in Maine are being primed to be reduced to laborers again at a modest fraction of minimum wage. Wages go down for and taxes (i.e., cost of living) go up on the working class while the income of the uberwealthy increase ten to a hundred fold in just a couple short decades. Power is consolidated and the fact that these people are getting away with the dissection of entire nations without penalty is significant evidence to that fact.
Sorry to go on and on; it's just kinda important to me. I, at the very least, and glad to see every day people standing up for themselves now that it's dawning on them how bad the GINI index in this country is getting. It's even worse than china.