Domino's great strength has always been security. But according to latest tests, Anonymous is not added automatically when creating a new database.
Adding Anonymous with "No Access" as default for new applications will cause no backwards-compatibility issues. But it will promote best practice and ensure "opt in" vs "opt out" security - developers and admins have to specifically allow Anonymous to access the applications rather than specifically revoke Anonymous access.
This promotes best practice amongst existing admins / developers and minimises security risks through ignorance from those new to the platform.