In reply to Ajay.

The questions I would ask to determine if social content sharing links are appropriate in a Theme:

1) Are they related to presentation of user content, or are they related to site functionality?
2) Would the user have a *reasonable* expectation that they would be retained when switching Themes.

Social content sharing links are functional, not presentational. They're (generally) completely agnostic to the Theme. And users *do* have a reasonable expectation that they would be retained when switching Themes.

IMHO, social content sharing links fall pretty squarely in Plugin territory.