Here's the social-networking code:
Basically provides minimal share code at the tcl level. The icons are not in CVS, but refer to ones on each of the social website vendors in order to not introduce non-GPL'd code into CVS.
Another useful proc provides a way to add default meta tags, when one or more of them are not defined at the page level. template::head::defaults_meta was briefly in CVS head at: http://cvs.openacs.org/browse/OpenACS/openacs-4/packages/acs-templating/tcl/head-procs.tcl?r2=1.18&r1=1.17
It is a separate proc so as to not change the existing functionality of template::head::meta, which I think would require a TIP. defaults_meta adds the meta tag, only if the meta tag is not yet defined, whereas meta proc overwrites an existing tag.
I'd envision a social-networking package providing services for registration/login via other social-networking sites including OpenID, perhaps user tracking statistics in a manner that xowiki provides (optionally set via parameter) etc.