Tell this to the conservative libertarians: Just like a city with no police, capitalism without existence and enforcement of rules to keep things competitive is unstable. Soon it would no longer be capitalism, but monopolism.
And don't say "regulated", say "policed". The word "regulation" has connotations of strangling, inefficient bureaucracy. The trucking industry in the US was a prime example of this. Used to be the US government ran this weird system in which the destinations and even the routes trucks were allowed to take were tightly controlled. Lead to stupid stuff like trucks being routinely sent on much longer trips than necessary. For instance, a company might own the route from D.C. to Pittsburgh, and Pittsburgh to Philadelphia, but not D.C. to Philadelphia. Any time they wanted to transport goods between D.C. and Philly, they would have to go 4 times as far as needed, so they could pass through Pittsburgh. Another problem was the acquisition of routes with intent only to block a competitor. Rather like a telecoms company trying to sue small cities that want to set up their own Internet service, for "unfairly" competing with it when the company itself is refusing to serve the community because it isn't profitable enough. It was a thoroughly artificial system. There was no sensible reason trucks couldn't take the direct route-- nothing like the roads being inadequate for truck traffic, or reserved for other uses. Thems was just the rules. Those sorts of restrictions should have a familiar flavor: the flavor of DRM.
Just what and how to police the market is the question. Should Microsoft be split, as the courts ordered? Some have used examples like the above trucking regulation mess as reason to push for the elimination of all policing of the markets. These are usually interests who think they'll win the monopoly game if allowed to try, or haven't thought of the consequences if they get what they think they want. They should read up on the history of capitalism in 19th century US. T. Roosevelt was one of our greatest presidents thanks to his anti-trust efforts. Railroads already had natural monopolies, and used this ruthlessly to gain ever more power and control. Sometimes though, it didn't work because the shark met a bigger shark, and some found themselves at the mercy of, say, an oil company attempting to monopolize its field. Standard Oil forced some railroads to give them kickbacks, and more. Ultimately, such railroads lost their independence, becoming puppets of the oil company, which found it all the easier to extend their power and control because the railroads had done a lot of the same work, for themselves. Or sometimes they'd see that cooperation and collusion was better than trying to break each other. Another area they found collusion useful was in "negotiating" with workers. One of the sickest things is the screaming of the opposition whenever the government proposes to raise our very low minimum wage. The companies only see that they are saving money if they all collude to lower wages as much as possible. They may see that they wreck the middle class if they get away with that, but they can't restrain themselves. They feel their survival depends on doing what others get away with, no matter how damaging to society. They actually like policing for that reason. They're just fine with rules that prevent destructive competition.