We've recently noticed that on June 13th, Stack Exchange removed the share buttons from the left side of questions on the network. The developers do not plan to add them back.
We believe that sharing questions on Project Management Stack Exchange is critical to promoting a broader interest in the site as a whole. It's up to our community to spread the word and help bring more experts and enthusiasts into our community.
I did some searching, and I found a StackApps UserScript that will add the share links to the "link" box that appears below questions. It's easy to install. I literally clicked "Install" in my Google Chrome browser and was instantly able to share a question on Twitter.