I'm trying to change the DB structure so that it allows universal terms that applies to all users and private terms for individuals.
I'm considering two options:
1. inserting a user_ID field in the existing terms DB to allow identification of private terms within the terms DB (this will store universal terms and privates terms in one set of terms DBs)
2. creating another set of terms DBs (terms + term_relationship + term_taxonomy) with a user_ID field to handle private terms only
'1.' will be simpler in terms of the DB structure but I wonder if it would be scalable (assuming that each subscriber will want to create their own terms taxonomies)