Google+/username

About

Unlike many other social environments on the web, usernames on Google+ are not a unique identifier but instead are expected to represent either the user's legal name or a name by which most people call them. (See Issuepedia for further discussion.)

The Google+ "edit profile" feature also states that if you change your name, you can't change it again for at least another four weeks -- and that any name changes are subject to review. The (often unwanted) tight coupling between Google+ and GMail does, however, provide an apparent workaround for this.