Facebook is too tightly coupled with the portal. At present we are dependent upon FacebookUtil remaining in core because of the following references.
In addition, it is tightly couple with /portal-web/docroot/html/portlet/portlet_configuration/edit_sharing.jsp
This JSP would need to be made more extensible so particular sharing options (like Facebook) can be contributed by other modules. One possible solution is already implemented for Portal Settings's authentication configuration JSPs. See