When I publish a news in my site, I do share the news in my Google+ account and Google+ Page account. 3 months ago, I noticed in the Google Webmaster Tools "Links to Your Site" section, that I got a total of 1413 backlinks from plus.google.com
All 1413 backlinks came from only 18 URL's that I shared on Google+. All of the backlinks are still listed in my GWT account.
A high value link to your site from another site is a link that recommends your site to the visitors of the other site because your site has useful information or content that they want to share with their visitors.
Links you create on social sites are not high value links. If that were the case, all you would need to do to rank at the top is to spend some time adding your links around the net. Whoever manages to litter up the net more than the next site would be at the top.
A few good, honest inbound links can make a bigger difference than thousands of low value links.