The value of a telecommunications network is proportional to the square of the number of users of the system.
— Robert Metcalfe

This law explains a little of the remarkable power of a growing network. Each time you add a user, or node, to the network, the number of connections increase in proportion to the square of the number of users. So, in this simple example where every new node gets a connection to each of the existing nodes, you can see that, say, adding a single node to an 11 node network creates 11 new connections.

It’s a simplified example because in most networks the value is not directly proportional to the number of connections as some connections or users may be more valuable than others, and usually adding a new user wouldn’t create a connection to all existing users — say if it was in a different country, or people spoke a different language, or just cared about different things. But nevertheless, you can see how a network quickly becomes valuable as users join.

So, Facebook has about 2 billion users…

Metcalfe was talking about telecommunications networks and the basic proposition has been modified since it was formulated including by Metcalfe himself.

Once again, just because something is called a law doesn’t mean it is one. See Fitt’s Law

Metcalfe’s Law

I’d idly wondered all my life, but never bothered to look it up. Turns out there doesn’t seem to be one clear accepted origin of Boxing Day, but the general premise goes that on or before Christmas Day people would give gifts to people of the same social level or class. On what used to be the first weekday after Christmas, but is now the day after Christmas Day, upper social classes would, in some form, give gifts to those in lower classes — often a Christmas box. This might have been because they had worked for them during the year in one way or another, like giving a Christmas tip to the milkman, or simply as a gift, or because the lower classes were too busy serving the upper classes on Christmas Day and so couldn’t do the Christmas thing properly themselves.

As is often the case, the Snopes article about Boxing Day, has a useful synthesis.

Origins of Boxing Day

The name for the troubling observation that where windscreens used to be covered in squashed bugs after a long drive, these days you’ll tend to see your windscreen remains squashed-bug free.

It’s believed this reflects a real and significant decline in insect numbers. Though tracking insect numbers is, however, rather tricky as you could imagine. So don’t ignore bugs, or treat them as pests, value them and, if you have a garden, try to provide some habitat to help them out. Here’s a good article about the windscreen phenomenon.

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The Windscreen Phenomenon