The default setting is for profiles to be seen by everyone (that means Google too).  However, if you are not happy about being public, you can easily change your privacy settings so that your profile can only be seen by a select few or only by you.

Click “Settings” in the menu at the top of the page, then choose the “Privacy” button.  Decide who will be able to see your profile and then click the “Save Changes” button to make it so.

Remember though, if nobody can see your profile at all, then there's not much point being in a social network.