Great radio program about the science of Emergence.
The example of how ants are able to find things through a positive feedback loop is fascinating. Essentially disorganized ant colonies are able to find food through such a simple mechanism. One ant that stumbles on food by accident will mark their trail with a scent. This scent will attract another ant who will also drop some scent. This will attract more ants which will in turn draw more ants.
I'm sure the growth of sites such as craigslist, Ebay and especially Friendster undoubtedly arose in popularity on the internet equivalent of this. Sending a site to a friend via IM or email is the internet's version of ant 'pee.'