It’s also much easier for Google to build a comprehensive profile of you based on your search history, your correspondence through Google services, and the media you upload. If you're not comfortable sharing private information with anyone who has access to the Google servers, the company makes it pretty easy to dial back the amount of personal data you’re sharing (or even go cold turkey) if you know where to look.
Of course, if you just want to make your Google account more secure, you can employ plenty of tweaks to make it difficult for anyone to hack your account and sneak a peek at your personal data. If you also want to ensure that you’re sharing as little identifying information as possible while browsing the web, simple changes such as opting out of personalised ads or clearing your web search history can help to keep your private data off the grid.
To bolster your online anonymity even more, you’ll have to take drastic measures and start deleting your Google service accounts. While it is possible to shut down parts of your Google account selectively while keeping others intact (cancel your Google+ account while maintaining your Google Reader list, for example), you should probably delete your Google account entirely if you’re concerned about data privacy.
Before you do that, consider taking advantage of Google’s Data Liberation Front to download all of your documents, photos, and other personal data from Google’s servers.
And while you’re at it, don’t forget to remove your home Wi-Fi network from the Google Maps location database, as well as to change your browser’s default search engine to Bing, Yahoo, or another search provider you feel comfortable using.