Logically, I would have to believe a Google+ share would be more valuable than a FB or twitter share from the viewpoint of the Google Search engine. But, I get the impression many site owners focus more on acquiring shares on FB and twitter, and seem to ignore Google+. Why is this?
many people share on fb and twitter due to traffic. people are used to these sites and google plus is not popular like fb and twitter. Google crawl google plus posts but it doen't crawl every post of fb and twitter.