There are many theories of human behavior that can be applied in this setting. Lawrence and Nohria’s book “Driven: How Human Nature Shapes Our Choices” (http://www.amazon.com/dp/0787963852/) might be worth considering, too.

Their book considers four key drives at the root of our behavior:

* to acquire
* to bond
* to learn
* to defend

Transcribed into Twitterish, we could set it up as such

* to acquire – a following
* to bond – with one’s brethren, find allies and bond with those more popular than oneself (the “cool by association” trick)
* to learn – it’s hard to come up with a snarky comment about that
* to defend – “staying in the loop” might work here.

However, let’s remember that human behavior is governed in part by physical laws (you can only be in one place at a time, etc) and the Dunbar number with relation to maximum group size (it’s not precisely 150, of course). Tools such as Twitter (or, more precisely, interfaces such as Tweetdeck) affect some of these boundaries.