You may have seen this article in the NY Times about a change to the Google Terms of Service and the reasons for it. Google wants to take your +1s and use them in ads, as "personal endorsements." The terms of service change enables Google to do this without your explicit consent for each use.
You can opt any existing Google accounts you have out of this policy and you have some time to do it.
Here's what you do.
1. Log in to your Google account (say, sign in to Gmail).
2. Click the icon representing you in the upper right-hand corner of the screen. For example, I would click the little photo of Marina Tcherkaskaya that I use for my profile photo:
3. Click Account.
4. In the left-hand menu, click Google+.
5. Find the line Shared Endorsements.
6. If the value is Off, you're fine - your +1s, etc. will not be used in search ads as endorsements.
7. If the value is On, click Edit.
8. Read the explanation, if you care. It includes examples of what this looks like.
9. To turn Shared Endorsements off, scroll down to this line:
10. Uncheck the check box.
11. Click the blue Save button.