Google has accused that Microsoft has used the Suggested Sites Feature in IE8 and Customer Experience Improvement Program in Bing Toolbar to send the user's search results data in the Google to Microsoft. Can also use other methods for a user's search results on Google can be traced by Bing.
But Microsoft denied the allegations. Microsoft says that the Google's accusations is a form of their anxiety to the popularity of Bing search engines. Microsoft noted that Bing experiencing significant growth. Google realized it and began to feel anxious.