In Howard Rheingold's Smart Mobs, there is an interesting discussion of how the value of networks increases exponentially as new nodes are added, Reed's Law. In the five years since Rheingold's book was released, Reed's law has been proven again and again.
Wiki's have surged in popularity in recent years. One of the main reasons is Reed's Law. While it may not be apparent at first glance, Wikipedia is a social network. Different authors collaborate on articles, linking them to other articles. Behind the scenes, authors and users discuss changes to the article.
Wikipedia had to have started as a single page. Let's say that article was "France." By itself, that article have very little value. But when someone creates a "Napolean" article linked to "France, and in turned linked to "Corsica." As the number of articles on Wikipedia increases, the value of each article increases exponentially. How many times have you gone exploring on Wikipedia starting somewhere like "Washington, D.C." and ending and following a trail of articles to "The War of 1812" and reading about when the White House was burned? Wikipedia is a social network of encyclopedic information that works as describe by Reed's Law.
Wikipedia isn't the only Wiki that acts like this. There's "how-to" wikis, comic book wikis, programming wikis, etc... Theres also a number of websites, like answers .com that use Wikipedia as the source for their content. The development of the wiki has made the internet even more valuable that it used to be.
It's important to think of social networking as more than just instant messaging and profile websites.
