Traditionally, in the era before the Internet and therefore before Google, when a person authored a work in print, it was automatically protected under copyright law (PDF). However, authors still needed to take measures to protect their words from others.
So, authors took precautions from printed theft by plagiarists in two ways. The first was to officially send a copy of an author's completed work, along with a check, to the United States Copyright Office. The second way, referred to as the poor man's copyright, was to mail a copy of the completed work to one's own residence and keep the envelope sealed. The postmarked date on the envelope would serve as a copyright stamp, unless the envelope was unsealed, of course.
Although those two ways are still appropriate for copyrighting printed material, the onset of the Internet has been a game-changer. Theft of an author's work is much easier nowadays; all it takes to lift someone's work is to highlight the desired graphic or text, and copy and paste.
With Google Authorship, online content producers now have not only some measure protection from online plagiarist but also a way to increase their search engine authority.
About Google Authorship
Google Authorship can be considered an online copyright of sorts, at least in sense that the author's online work from a blog, tweet, or website can be documented and tracked so the work does not disappear into Web obscurity.
Right now, anything that has been written on the Web that is not tracked by Google could be considered fair game for theft. However, if a writer registers his or her work via Google Authorship, the writer's work will be tracked by Google as having been authored by that person, so the theft of that work becomes more easily traceable.