I did a similar study of traffic solely attributable to a single post on ReadWriteWeb. I wrote a technical paper with the results: http://www.stinkyteddy.com/

I did a similar study of traffic solely attributable to a single post on ReadWriteWeb. I wrote a technical paper with the results: http://www.stinkyteddy.com/documents/SocialMediaResponse.pdf http://www.stinkyteddy.com/documents/SocialMediaResponse.pdf The long tail traffic is well described by an exponential function with a "half life" of about 10 days. You should check your data to see if that number is universal.