Left-libertarians often seem to argue that even just a little bit of statism so distorts markets that the results produced by the mixed economy bear little relationship to what a freed economy would produce. Just as putting one drop of a liquid one owns into an unowned lake does not make the whole thing yours, neither does one drop of statism suddenly mean that the results of a mixed economy are vastly different from the results produced by a freed market.
I've got two problems with Horwitz's formulation.
The first is that there's never just a "little bit of statism" involved, nor, in my opinion, can there be. The evolutionary trend of the state runs in one direction: Toward more -- and deeper -- economic intervention and regulation. Rollbacks of state economic intervention/regulation are the exception, not the rule. Since the birth of the Westphalian nation-state, nearly every state has been, at nearly all times, progressing toward, not away from, total statism.
The second is that even little interventions which only slightly change the direction or velocity of a thing can result in very large effects over time. If you don't believe me, take off from Jefferson City in a small plane and fly 1000 miles due south, then 1000 miles at 20 degrees east of due south, then 1000 miles at 20 degrees west of due south. You'll find yourself in three very different places (very roughly, Baton Rouge versus Austin versus Tallahassee).
Contra Horwitz, I regard things like state-mandated limited liability for corporations as having likely produced long-term growth a) in very different directions, b) to much greater proportions and c) among particular entities, which would not have gone those ways absent the surplus profits created by the state miracle-ing away the need for investors to insure versus liabilities connected to their portfolios.
Unlike many left-libertarians, I'm less cocksure in my claims about precisely where things would have gone absent state intervention, or my predictions concerning precisely where they might go if the state disappeared this afternoon ...
... but I think it's reasonable to hypothesize that things economic would look very different today absent (to take three English economic interventions of past centuries because they're handy to my thoughts at the moment) the Statute of Anne, the Inclosure Acts, and the state privileges granted the East India Trading Company) ...
... and that it's reasonable to hypothesize that if Murray Rothbard's "destroy the state" button got pushed today, things economic would look a lot different a century from now than they will if, as I expect, the state continues to totter on for awhile longer.