Removing copyright law and trade secrets removes almost every monopoly
Incentive remains as evidenced by open software and open standards in many industries.
The only thing left is to heavily regulate mergers and buyouts. Price fixing becomes a non-issue in almost every market since there are no patents and secrets. That leaves a few industries like raw resource handling (oil,diamonds,food,etc) in which you just force splits so no one monopolizes the good.
The problem is the government sucks at doing the most basic thing! Monopolies are allowed to exist (telecom, Microsoft, gas). The most basic regulation possible, that of busting up monopolies, isn't even done. Then the government goes and throws thousands of other regulations that drown out the free market (huge subsidies, bloated contracts, wildly overzealous safety standards in response to freak accidents, etc, etc).
Meh, I wish I was dictator for a year so I could mess around and experiment with some real policy. I don't think anyone in DC actually knows what they are doing. We don't have a free market or a socialist one. It's some weird twisted market where the government enforces monopolies through overly long patents and copyright law, in which simple regulation isn't enforced, and where hundreds of little regulations drown small business and outsource industry.
People can go on about economic theory all they want. We have a screwed up economy and no one knows what fixes it. People just implement policy until it reverses, and then claim after the fact that their policy fixed it. It's a viscous cycle, and I can't help but feel that we bleed money from inefficieny in our economy.