Exactly... Nielsen looks at EVERYBODY, because there's a market for everybody's information.
Furthermore, it's a joke to think that Google is going to compete with Nielsen as **Google sells advertising**. This is not an unbiased source. The reason that Nielsen even exists is that [insert Ford, Apple, or any other buyer of advertising time here] is not going to take [insert NBC's, Comedy Central's, or any other seller of advertising time here] word for it about how many people are watching their shows. Apple wants to hear from an unbiased souce that X million people are watching ABC during the period for which Apple is buying advertising time.