If I remember correctly (my memory is getting foggier by the minute), the user_demographics stuff has never been implemented in a publicly released version of the ACS toolkit. It's just crufty code from the Paleolithic Era.
Occasionally and unintentionally (we presume), code customized for an ArsDigita client makes it way into the source tree. The data models for both the pets modules (www.pogopet.com) as well as the photodb module (www.photo.net) appeared briefly in ACS releases, only to disappear in a subsequent releases. (Yes, I know the photodb module has now released for general consumption.)
Since this question has been repeatedly asked on the web/db forum at www.arsdigita.com, one can safely assume that ArsDigita has no plans to release the Tcl procs that support the user_demographics table.
