"Intentional or not, the engineers who made Google+ built it for SEO. Consider the factors that make sharing content on Google+ far different than sharing on other social networks:
1. Posts are crawled and indexed almost immediately
One of the original goals for Google+ was using it to power real-time search after Twitter cut off Google's firehose access to its data in 2011. Since then, Google has been using Google+ to discover new content, and many web professionals have discovered that URLs shared on Google+ are crawled and indexed very quickly.
Compare this to Facebook, where because of privacy settings and restrictions on data sharing, it's not uncommon for posts to never be crawled or indexed by Google at all.
Unlike Facebook, which hides data from Google, or Twitter, which directs Google not to follow most of its links, Google+ data is immediately and fully accessible to the company that built it.
2. Google+ posts pass link equity
Pages and posts on Google+ not only accumulate PageRank, but because links to posts are followed, they pass link equity on as well.
When you share a link on Google+, the anchor text becomes the title of the page you are sharing. Some important things to remember about followed links within Google+:
- Only "shared" links (the links that show up beneath your post) are followed. Any external links you add withing the post body itself are nofollowed, so these don't pass any link equity.
- For obvious reasons, uploaded images don't pass external link equity. Some people like to upload a screenshot of a page and then link to it in the body of the post. While a good image may increase post popularity and click-through rate, these posts do not pass link equity.
- Certain links in your Google+ "About" page are also followed and pass link equity.
3. Google+ is optimized for semantic relevance
Unlike Facebook or Twitter, each post you make in Google+ has most of the characteristics of a full-blown blog posting.
- Each post has its own URL.
- The first 45-50 characters of the post appear in the title tag.
- Just like a blog post, entries can be long and complex in order to explore a subject deeply. Various correlation studies have show a strong relationship between longer pages and higher rankings.
- If a post is reshared, it can accumulate internal links from the Google+ platform, all with relevant anchor text.
- Because of these factors, each post has the potential to send strong semantic signals to Google's search algorithm. This not only helps the post itself to rank in Google's search results, but potentially sends relevancy signals to a URL shared by the post.
Taking advantage of Google+ for SEO
While there are hundreds of ways to optimize your Google+ experience, the most important activities can be summed up by these nine points:
1. Start building relationships now on Google+
It's never too late to start. Google+ is a social network. Following great people, commenting on posts, and sharing great content not only helps to increase your own influence, but it can be extremely educational as well.
2. Post share-worthy content on Google+ to attract natural links
When you share content, don't just post a link and walk away. Add additional value with commentary and relevant information.
Consider these examples of long Google+ posts. Each acts like a mini blog post and adds highly shareable, linkable context. I don't recommend replacing your personal blog with Google+ entirely, but sometimes a few lines of context makes all the difference.
3. Add Google authorship information to your online content
Adding rel="author" to your website is a no-brainer. If you guest post or otherwise contribute content to other high quality sites, ask the publisher if they will add author markup to your bio. Kane Jamison recently did this for me when I contributed content to his blog.
4. Link out to all relevant profiles from your Google+ "About" page
Think of Google+ as a primary hub of your online virtual identity. Google offers you several places to link to other online profiles, sites that you contribute content to, and simply sites that you want to share.
5. Take advantage of rel="publisher" by connecting your website to your Google+ brand page
6. Make your content easy to share on Google+ with relevant social sharing buttons
You would think everyone wants to add social sharing buttons to their content, but some folks are just stubborn. Don't be stubborn.
7. Completely fill out your Google+ profile with relevant and engaging information
The information you provide in your profile influences how you show up in Google+ search results and also plays a role in whom Google suggests others to follow.
8. Make it easy for people to add you to your circles
Use Google's easy-to-create badges, or create your own to place on your own online profiles so that others can easily add you to their circles.
9. Make your posts public.
Posts shared privately don't pass the same juice as publicly shared post. For SEO purposes, you likely want your posts spread as wide as possible. Philipp Steuer made this great Google+ infographic simplifying the complexities of who sees your posts:
Additional resources for success
Entire books can now be written on using Google+ to boost your SEO efforts. In reality, there are exactly 3 articles that contain 99% of everything you need to know:
Google Plus SEO: Everybody Talks About It – How Do You DO It? by Mark Traphagen
Google+ SEO by AJ Kohn
10 Dead Simple Tips to Take Advantage of Google+ for SEO"
Many thanks to Cyrus for this helpful post. And, btw, the article has a "Follow Me" button so that you can keep up with the information Cyrus shares, along with graphs, images and comments that I didn't copy here.