Google+ and other sharing sites were rmoved in the recent design change.
According to a Jason Menayan, the director of marketing.
"Those who regularly use services like Stumbleupon tend to use browser buttons and other features that enable them to be shared with those communities. We have buttons for Facebook, Twitter and (if not opted out) Pinterest, since these are, by far, the largest sources of social traffic to HubPages."
I respectfully disagree with the assertion that people who use social networks other than Facebook and Twitter are more likely to use "other features" and interestingly I am staring at the +1 button on your question above but we don't get the same help on our articles.
(I little editorial to go with my answer.)