Some glorious and fascinating reportage-porn at memetracker that shows how news stories are taken up and how long they last and what their impact is:
They found a consistent rhythm as stories rose into prominence and then fell off over just a few days, with a “heartbeat” pattern of handoffs between blogs and mainstream media. In mainstream media, they found, a story rises to prominence slowly then dies quickly; in the blogosphere, stories rise in popularity very quickly but then stay around longer, as discussion goes back and forth. Eventually though, almost every story is pushed aside by something newer.
There is something truly wonderful about seeing this information laid out in such an intuitive manner. This kind of analysis of the growth, spread, and retention of ideas is certainly an area that will expand and grow over time.