Google Search is not just about searching for terms, they also have a Phonebook search, which allows users to lookup phone numbers of users.

You can lookup any numbers of users by visiting the Google Phonebook Search, or by typing the phone numbers directly in Google search. Google search displays the name of the user who owns the phone number and the address with a link to a Map.

You can also append the phonebook operator to your search queries to directly search Google phonebook, for example if you want to lookup phone numbers for Bill Gates, the search term will be “phonebook:Bill Gates”, typing this query will directly take you to the Google phonebook search page. Try this search query by clicking on this link, phonebook:Bill Gates.

If you paranoid about privacy and want your phone number removed from this list, visit the phone number removal information page.

Google Phonebook Search [via Google Inside]