/System/Library/PrivateFrameworks/SocialLayer.framework/sociallayerd.app/Contents/MacOS/sociallayerd When sensitive social UI elements (such as contact photos and names) are displayed in an application via SocialLayer.framework, that application should not have access to the contents of those elements. In order to protect users' private information, the actual layers for those elements are generated by sociallayerd, while keeping them out of the app's address space. CoreAnimation can then render the sensitive layers together with the application layers.
The binary is a part of sociallayerd application.