I like to keep an eye on the Schneier on Security Blog. Usually there’s some interesting information. While the post I am commenting on here does not seem like a natural security topic — it rather seems the security aspect was forced on it — it is a very interesting post simply for its theory about optimal human group sizes for various scenarios and social situations. While I am certainly no expert on this, the numbers given sound very reasonable and correct based on personal experience.
More generally, there are several layers of natural human group size that increase with a ratio of approximately three: 5, 15, 50, 150, 500, and 1500 — although, really, the numbers aren’t as precise as all that, and groups that are less focused on survival tend to be smaller. The layers relate to both the intensity and intimacy of relationship and the frequency of contact.
The smallest, three to five, is a “clique”: the number of people from whom you would seek help in times of severe emotional distress. The twelve to 20 group is the “sympathy group”: people with which you have special ties. After that, 30 to 50 is the typical size of hunter-gatherer overnight camps, generally drawn from the same pool of 150 people. No matter what size company you work for, there are only about 150 people you consider to be “co-workers.” (In small companies, Alice and Bob handle accounting. In larger companies, it’s the accounting department — and maybe you know someone there personally.) The 500-person group is the “megaband,” and the 1,500-person group is the “tribe.” Fifteen hundred is roughly the number of faces we can put names to, and the typical size of a hunter-gatherer society.