The sharing buttons were recently removed because a lot of people hated them and few people used them. In the words of Kevin Montrose, Stack Exchange developer:
18 hours of data under the new rules plus historical data of the old scheme, reveals that in fact the share buttons are pointless.
About 90% of the people who bother to share something on Twitter/Facebook/G+ copy/paste, and the amount of traffic referred from social media (to Stack Overflow or any of the Stack Exchange's) is far too small to dedicate that kind of real estate to.
Plus everyone hates share buttons, they are the herpes of the internet.
