A few months ago, Akamai Senior Enterprise Architect David Senecal wrote a post about ways to identify and mitigate unwanted bot traffic.
Last week, I went into more detail on the subject with Matt Ringel (@ringel on Twitter), an enterprise architect in Akamai's Professional Services team. (Check out Matt's recent post, "You Must Try, and Then You Must Ask."). That resulted in the post "Bots, Crawlers Not Created Equally."
In addition to that post, we have a full audio recording of the conversation. Listen to it HERE.