Stowe Boyd talks about something he calls Social Architecture:

Authors and readers both leave social traces behind (or "gestures"), as a result of their activities. Authors point to other blogs in their posts - either by link or by name - and create ageless links like blogrolls: these represent an implicit social network relationship between the parties, not just a topical pointer, like a search engine provides. And the actions of readers (which includes all authors) create similar gestural information: explicit, shared evidence of reading like comments and bookmarks, and implicit value indications, like the frequency of return to a specific blog, or the number of comments left.

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Machines -- software applications, like Google or Technorati -- "read" the blogosphere, too, although not in the way that people do. These apps are plowing through the blogs, indexing the text, and, on the social side, algorithmically evaluating the value of various blogs or blog posts based on the social cues that readers and writers have left behind, as well as less social analysis, like keyword incidence.