This recent Moz article claims that there is a connection between +1s and high search engine rankings.
I see these types of “correlation vs. causation” debates, studies and articles all the time as those within our industry are always looking to reverse engineer the Google algorithm. My reaction is this: while +1s / posting on Google+ is beneficial to your overall SEO effort, neither is a magic bullet.
Exceptional content that is promoted well on social networks generates social signals, which are a known part of the Google algorithm.
The author may have jumped the gun a bit. He’s since edited the post to clarify that posting on Google+ has SEO benefit and not +1’ing posts.
Now in 2013, there’s strong reason to suspect it’s different with Google+, and that the relationship between +1s and higher rankings goes beyond correlation into the territory of actual causation. (Edit: This should say “posting on Google+” instead of Google +1s. It’s clear that Google doesn’t use the raw number of +1s directly in its search algorithm, but Google+ posts have SEO benefits unlike other social platforms.)
I predict that, moving forward, who +1s your content will become more important than how many +1s you have.
We already know that Google personalizes search for logged in users. And we know that Google crawls users Google+ profiles and has the ability to monitor their activity (what types of content they +1 and which articles they comment on as a logged in user). We also know that Google wants content creators to use authorship markup on their posts and wants publishers to use publisher markup. Combine the above will all the data tracked and stored (anonymously or not-so anonymously) by the Google tracking cookie and Google knows a lot about its users.
At some point, this data may replace traditional ranking factors such as inbound links, as this data is not as easily manipulated.
I’ve said it before, Google needs Google+ to work and this is just one example of how it already does.