Via Nature (via Smart Mobs), news of a study that says if you haven't seen a news article within 36 hours of its publication, you're probably not going to see it:

Dezs and his colleagues collected such data for a single day on the Origo portal, during which time it released 3,908 news stories. On a typical day, Origo logs a total of 6,500,000 hits. The researchers looked at the relationship between the number of hits per item and the date the item was released, as well as the patterns of visits to the site by individual users.

Unsurprisingly, each item receives the most visits on the day it is posted, and the number of hits falls off rapidly after that. There is a daily rhythm because nearly all readers of the Hungarian site are in Hungary, so hit patterns are not affected by having readers in different time zones. After just three days, most people who are ever going to read the item have already done so. Even with an archive, online reporters cannot pretend they are writing for posterity.

You can find the original research paper here