If you are still trying to stick with pure SEO only you will be in trouble. Your Google SERP is not the only way to get traffic now. Not anymore. Even to rank in Google now social signals are a big factor. Google+ probbly going to be an important pointer for Google ranking in future. Also search engines can't ignore other social signals like link popularity in FB etc.
There are several good articles in searchmetrics.com showing why these Social signals are important. you can see in this graph how ranking factors work.
There is very good study you can download from their site and Which can give you some valuable information about this whole subjectCode:http://www.searchmetrics.com/en/services/ranking-factors-2013/