For Enterprise/Business tier, create an admin toggle that disallows user sharing of snippets outside of the organization.
Agreed this would be useful. Another toggle we're looking at is an option prevent org members (non editors and owners) from being able to create their own snippets (to enable the enforcement of a top-down system for snippet definition and usage).
Just a quick update that this feature has launched. Organization owners now have additional controls over snippet sharing and snippet usage. Sharing outside your domain can now be disabled.