When you log into a web site, using your Google account, you give that site access to some of your personal information. Maybe it’s just your name, or email, or more, but still, it’s access.
You should try and get into the habit of clearing these out on a regular basis. It just takes a few seconds, and you can quickly revoke access to the left overs. Sites you use regularly should be left in tact.
My rule is …. weekly. If I visit a site at least once a week, then I want the authorization to stay. Less than weekly, is easy enough to click that “yes, i agree” button when that site needs access.
Enjoy!
http://scottcate.looplogic.com/clear-out-unused-authorized-sites-from-google-account