I read a fair amount of pop-econ and pop-psych. For instance, Malcolm Gladwell's excellent books, such The Tipping Point, and recently, Outliers. I recently read Chris Anderson's Free, breaking down the potential of companies (or bands) to make money by giving stuff away.
It's interesting to see some topics arise in several of these books and one I've seen in the above - and in some other articles lately - is Dunbar's Number.
In basic terms, Dunbar's Number is 150 - being the maximum size of a given person's true social network. The number was established through research... of course there is some dispute that 150 is the number, but, Dunbar did notice some interesting things. You can find plenty of examples through history of societies that broke apart into two groups when their total populations exceeded 150. Roman army units were made up of 150 soldiers.
The idea is that, once you exceed 150 people in a group, cohesiveness - or common mutual interest - begins to erode. (Warning: that is also an oversimplification).
Most of us, these days, have much larger social networks. I have, somehow, 346 friends on Facebook.
But in reality, do I correspond with all 346? No. It is much easier to keep up to speed on folks. I am happy to know how some people are doing that I don't often talk to. It saves long "catch up" chat that existed before the advent of online social networks. All that is grand.
But functional social groups, I have decided, cannot be so big. Think of a wedding party. Small weddings tend to result in one common experience. You ask my friends about my wedding, they probably tell the same story. Now think of a 350-person wedding. The room divides itself up, partially because, well, there are so many people you don't need to hang out with those other people. Your experience at the wedding is likely different from those of the folks on the other side of the ballroom.
None of this means you should have a certain kind of wedding. The point is, we have limits in our abilities to relate to one another. There is point where you stop caring about the needs of some others because your own self-interests can be supported by an entirely different group.
And once again... this isn't bad. Life would be tiresome if we were always forced to act strictly in the interests of a group. We're not stranded on a desert island. But it's valuable to think that due to the number of people we interact with, we tune out some and put extra emphasis on others. That doesn't lead to a complete view of anything.