Learning from facebook, Google+ is using the tagging feature which can be turned on in the Settings Page. By default it is automatically disabled. Google+ is calling it "Find My Face".
Google+ has also added a auto suggestion feature as well which of course makes it easier to tag photo's. Google+ has disabled this feature by default to protect certain user's privacy, for example: You go on an interview for a job and the potential employer looks you up on the major social networks and see's a picture of you passed out with vulgar writing on your forehead.
Google+ will be using data from Picasa Web Albums for the Face Recognition suggestion feature.
Local Business Website Design, SEO and Internet Marketing Blog
By "Shawn Lippert"