diberry - 4:30 pm on May 19, 2013 (gmt 0)
I believe Google thought they could leverage their search dominance over us webmasters to force US to promote it for them. A lot of webmasters have complied, and still it lags behind. It's just not going to work.
I don't use it at all for my sites. I considered it, but I just can't see an ROI on my time and energy. I have buttons on one site so visitors can share my pages with Google+ or a variety of other networks. The Google+ shares are nothing compared to the others. It just looks sad.