Website owners and administrators might have noticed a new search spider agent appearing in their site logs. It appears that Google has another bot operating out there.
Google MediaBot Indexes Web Pages
Google’s Matt Cutts confirmed that the AdSense Mediapartners bot, commonly known as “mediabot,” is indexing webpages for Google’s Big Daddy index, according to some well-known bloggers. What that means to webmasters: having two versions of a webpage (one for each bot) can get you into duplicate content issues.