I'm not a real big Google+ user, but I may consider changing my ways. I really like the "You shared this" feature and it integration with the Google's Author Information in Search Results. When you set everything up properly it leads to "effortless sharing" or at least given the latest change to Google's Social Posts in Search Results. If you want to be an influencer in the digiterati it might be time to reevaluate using Google+. These results are also transitive, even if someone isn't directly in your circle, if they are in one of your friend's circles you can still influence their search results and possibly take up one of the bottom results on the first search page.
A sample of what search results with social posts look like given my circle of friends:
This is a SERP for an article that was "shared by me", because I have a Google+ author profile link on my blog pages. I never had to share this article but Google can identify it as "shared by me"
Here are some friends of mine influencing my search results with very generic search terms that they would generally not rank on the first page of results:
Wayne Yamamoto for the search terms "social proof", at the time I took the screen shot Wayne had not shared this via Google+ but he can still pick up the last result in my SERP.
Kevin Leu for the search terms "Silicon Valley", Kevin usually shares everything on Google+ and is able to pick up 2 SERPS on the front page for Silicon Valley when I am logged into search.
If I am in your circle and you repeat these searches, chance are my friends can influence your search results.
Invest in your Google+ profile, it's like a Facebook feed in every google search.