David points to this chilling post at Media Guerrilla, where Mike Manuel outlines the 90 second news cycle:

+1 second to hit publish
+2 seconds for a blog to refresh
+3 seconds for feed readers to update
+4 seconds to email, link, tag, rank, or rate a blog post
+5 seconds for readers to form an opinion and/or leave a comment
+1 minute for Technorati to register a server ping, crawl and index a blog post
+8 seconds for alerts, watchlists and saved searches to propagate
+4 seconds for a blog post to plateau, amplify or disappear
+2 seconds for this cycle to repeat from the beginning
+1 second to realize the world’s changing…

If any of the terms above are unfamiliar to you… don’t worry about them.