I don't necessarily believe this to be a possibility... but if the US contracted out "security" to companies like Blackwater, it seems at least.... plausible that they could contract out "missile defense."

ICBM Delivery service? sign me up

Theoretically, they could be mercenaries, hiring themselves out to some corrupt dictatorship, guerillas, drug lords, state-sponsored terrorists, or similar groups. They would collect a bunch of money and launch a missile at their enemies. Turning that into a sustainable business model has ... hazards, of course.

The Economist had an interesting book review on a book positing a return to medievalism -- where the state does not have a monopoly of force -- and it's interesting: a little far-fetched and unlikely, but just this side of plausible. http://www.economist.com/news/books-and-arts/21638096-how-pr...

One notable bit was the incident where "a famous actress turned humanitarian [...] with various human-rights groups, wanted to hire Blackwater to set up safe havens in Sudan to protect civilians fleeing the janjaweed militia" but decided against it.

Space launch systems are so deeply dual-use it's not even funny. Orbital rockets are very similar to early, low-readiness ICBMs - modern systems prefer solid fuel, since they can be safely kept fueled for longer periods of time, but aside from that the biggest differences between a Falcon 9 and an ICBM is how ridiculously overpowered the Falcon is, and its lack of re-entry countermeasures (MIRVs, decoys, etc.). Which is why anyone working at a company like SpaceX is subject to the same technology export restrictions as weapons companies.

For example, if SpaceX can get e.g. the Dragon capsule to land with a reasonable accuracy on thrusters, and then put a warhead in it (or multiple warheads) , that's quite a capable weapons system right there. In fact, it's even capable of fractional orbital bombardment, which was considered so destabilizing during the Cold War that it was specifically banned in SALT II.

tl;dr - Elon Musk will, within a couple of years, control a system that can be adapted into an ICBM within a very short period of time and with minimal investment.

The best historical example is the British East India Company whose private army conquered India and ruled it for about 100 years. Another example is the United Fruit Company in South America that bought local armies to crush rebellions.

Since the US government has become so corrupt American companies have found it easy to use the power of the US government to coerce other countries, for example for intellectual property treaties. But it’s feasible that in the future companies might want their own military power to get their way.

It's basically the company-as-government idea, wherein a company is so big it begins to function like a government, including military operation to further its goals.

Which, tangentially, is the model presented by extreme libertarians as the way of the future and how we can do away with government for good.

Exactly. The irony here is intense.

What other options come to mind?