I think you're missing the point about laws and democracy. Libertarianism assumes you have the least possible government and preferably none at all. You don't really need democracy when you can vote instantly with your wallet and you don't need a centralized law-making body when everybody implements their own laws on their own property and various property owners are in competition with each other as to whose laws work better and generate more profit.
It always confuses me that on a site like HackerNews how ideas are promoted without serious thought into how they could be exploited, especially when they've been exploited over and over and over throughout history.
The model you are talking about is terribly easy for anyone with a sufficient lust for power to control. You see it all the time in Africa and the Middle East. Warlords gain a bit of power and start taking over territory and eventually build a small army. With said army, you take over transportation or simply rape and pillage.
Even without physical violence, economic control is equally possible with a sufficient monopoly (which, with no regulatory system to prevent dumping, tying, etc., isn't that hard to build). Control shipping, an important bridge, a major highway, waste disposal, etc. and you can effectively blackmail any of your neighbors' "sovereign" lands.
Unfortunately this is true. One of the defining moments in US history is when George Washington chose to resign his post as general of the continental army rather than use it to crown himself emperor.
The big question is would it have worked? Was the fledgling country so republic-loving that it would have overcame a despotic Washington?
In other words, how robust is freedom when the general populace really wants it (and has somewhat of the means to back it up)?
It's not immune, but governments tend to be formed with the mandate to prevent those exploitations. This makes them more resistant to those desires. The more people in that government, the more social pressure there is to keep those exploitations minimal so that they can remain undetected.
That's what the difference between a government and a business is. They are otherwise the same.
I don't see how staying in the office for 4 years practically indefinitely, makes you more resistant to exploit the opportunities it provides. On the other hand, when business does something customers don't like, it loses customers, money and goes out of business very quickly (unless it is bailed out by the government!).
Also, in my view, the problem with your argument is that your expectations of government (preventing exploitations) is rather different from reality (picking winners). Just because many people believe that government is supposed to do good, doesn't make it act this way.
A government has a much harder time being exploitative than a business does. To the extent that a government's personnel are involved in businesses, the government is corrupted and its resistance to exploitative desires will break down.
