Under new privacy rules that Google is implementing on March 1, all of the data that Google collects based on your usage of YouTube, Gmail, Google+ and Google search will be aggregated into one user profile.
And you can't simply click a button to opt out. Google's ability to collect this information, which they use to deliver targeted ads to the pages that you look at, is part of the bargain. However, there are ways to manage your privacy. (Watch a slideshow of how to protect your online privacy.) Here's what you can do: