According to the Washington Post:
"Google said Tuesday it will follow the activities of users across e-mail, search, YouTube and other services...
The information will enable Google to develop a fuller picture of how people use its growing empire of Web sites. Consumers will have no choice but to accept the changes.
The policy will take effect March 1 and will also impact Android mobile phone users, who are required to log in to Google accounts when they activate their phones."
Without the ability to opt out, this is a horrible invasion of privacy and an abuse of the trust its users place in Google. Although the ability to opt out is better than nothing, requiring users to opt in before Google begins its surveillance is much preferable and should be the choice Google makes before such surveillance begins.