While Google denies any direct relationship between Google Plus content and activity on one hand and SEO rankings on other, very often good ranking sites have good Google Plus activity. While in theory this could be pure coincidence, the results speak for themselves. Here are some reasons why Google Plus is especially important for SEO:
Google owns it and no matter if they admit it or not, as empirical evidence shows popularity on Google Plus is a huge factor for good rankings.
Some links are dofollow and they help to improve rankings. Not all links are dofollow but unlike on other sites, at least the so called “shared” links (the links under your post) are dofollow, so take advantage of that. Additionally, when you post something interesting that gets reposted, you earn multiple links to the same page.
Links from Google Plus get relevant anchor text – the title of the post is the anchor text (which obviously is much better than “Click this”, “Here”, or other generic anchor texts) and the best is that this anchor text sounds natural and won’t hurt your rankings.
Ultrafast indexing of all pages is another benefit. While it is true that Google is fast to index any site that gets frequently updated, the advantage of Google Plus over Twitter and Facebook where all or most of the content is hidden from search engines is hard to beat.
As you see, the benefits of Google Plus for SEO are really noticeable. So, even if you are skeptical about the whole this social media hysteria, the case with Google Plus is different and it will pay to give it a try, if you haven’t already done so.