Have you already read something like the link below?
http://en.wikipedia.org/wiki/Peer-to-peerAlthough the article needs some editing, it presents the ideas.
Let me put it this way. As a metaphor.
In the USA a major highway intersection has tragic lights to control the trafic.
In some countries they have e have a circular intersection.
In other places the have a tragic cop in the middle of the intersection.
Places that have non of the above are Ad-Hoc.Ad hoc is a Latin phrase which, literally, means "For this". It generally signifies a solution designed for a specific problem or task, non-generalizable.
In other words, near chaos. The piratical limit is about three or four computers.