At a recent lunch during the PubCon search engine marketing conference, unofficial Google spokesman Matt Cutts confirmed that there are two types Google spiders crawling the Web looking for indexable content for Google’s search index.
Firstly, there’s GoogleBot, the Google spider everyone knows about. Secondly, there’s MediaBot – the spider connected to Google’s AdSense program. There have long been rumours that having Google AdSense ads on your site helps improve your site ranking. According to Matt Cutt’s statements, that is most definitely NOT true – but it might help your site getting indexed in Google faster.
He also mentioned one thing that can get you into trouble real fast – if you serve different content to the two spiders (which could be done using a form of search engine spamming called cloaking). If GoogleBot is served different content to MediaBot, you run the risk of losing your listing altogether.
According to Matt, the reason for using both GoogleBot and MediaBot is the resulting savings in bandwidth costs for Google.