The Drupal memetracker module (admittedly pre-beta) uses Python's Pyclust. With Techmeme, linking is definitely part of it, but not all. I found this out when e

The Drupal memetracker module (admittedly pre-beta) uses Python's Pyclust. With Techmeme, linking is definitely part of it, but not all. I found this out when experimenting with Onespot.com a site that aspires to be, but is not yet, white-label memetracking. They cluster only on links, and as a result, have barely any clusters picked up. Aside: I think Techmeme does a much better job than Google News, it not only clusters, it kind of threads. Techmeme's Gabe Rivera, who jokes so much you can't tell when he's serious, has said that Techmeme "has always been biased," and I sometimes take that to mean not that it's biased in terms of what's "hot" (that's the political interpretation), but that it's biased in terms of what's a cluster. Techmeme also recently openly added human curation, but that's a separate level of intervention than the clustering we're talking about.