Folksonomies and yet more Flickr
On social software: I came across the term "Folksonomy" (referring to the categorisation of resources using tags in a flat namespace) for the first time. And my favourite Folksonomist, Flickr, "...get that that connection is meaningful, exceedingly meaningful, and if you can leverage that behavior, you can provide an experience orders of magnitude more interesting than when you ignore that connectedness."
More on the importance of social networks: "As physical space gets annotated with digital layers we will need some means of quickly sorting through the pile of bytes at the location to get a handful that we can skim through."