I like a political-economic metaphor: functions in the operating system are the equivalent of public utilities like water and power. If an economic sector has characteristics of a natural monopoly, is at a commoditized state of evolution with decreasing gains, and potential for unfair practices that require regulation, countries tend to consider nationalizing them or at least regulate them very heavily.

In fact you can get to a very detailed metaphoric mapping (example: memory management is like real estate title registration, multiprocessing is like traffic regulation, network management is like interstate commerce, the Web is like container shipping standards, TCP/IP protocols are a bit like the global financial system, security is like police/military/border control...).

Sectors can go in and out of public/regulated sectors. Ditto OS functions (example Dropbox can be considered a "deregulation" of the filesystem, mapping/location started as an application layer function but is increasingly turning into an OS-like function).

The metaphor is actually a good guide to analysis and synthesis. When big changes happen in technology paradigms, it is useful to re-examine what's in the OS and what's not. Application functions may need to be absorbed into the OS and vice-versa. In fact the only thing missing is a real currency-like artifact, and I am told some people think of Bitcoin as an economic-transactional protocol for computing rather than a real-world currency.

I recently learned about the Paxos system that's behind Google's latest innovations in distributed computing and there's a Leslie Lamport paper about it written in terms of a metaphoric political system. It's been on my to-read list for a while.

http://en.wikipedia.org/wiki/Pax...

Disclaimer: I am not a computer scientist. This is based on long-forgotten random reading of a couple of OS texts as an undergrad. I remember trying to explain the ideas to myself via such metaphors.