Publishers running AdSense on their pages may find that the Mediapartners-Google bot - the special Google bot used by AdSense to determine ad targeting on a publisher page - is actually sharing the results of those crawls with the main Google search database.
Greg Boser spotted it when pages being served strictly to AdSense began showing up in the main search database. And cache dates and times are matching exactly with when the Mediapartners-Google bot visited the page for ad targeting purposes.
How significant is this? At this point, it is uncertain, although Google clearly states that being an AdSense publisher does not help with search engine rankings. And it seems that the Mediapartners-Google bot is not adding new pages to the search index, but rather updating pages currently in the index.
Postscript: Matt Cutts has confirmed that the AdSense mediapartners bot is indexing for the main search index.
The Original Search Marketing Event is Back!
SES Denver (Oct 16) offers an intense day of learning all the critical aspects of search engine optimization (SEO) and paid search advertising (PPC). The mission of SES remains the same as it did from the start - to help you master being found on search engines. Early Bird rates available through Sept 12. Register today!