On-the-fly classification of domains, when enabled, happens for those domains that aren't already in the blockerDNS database. When a domain gets classified it's added to the database along with its category and the date. The date is included as a reference point for any potential future troubleshooting with the automatic classification system. Logging of a user's activity is done on a strictly opt-in basis. With regards to instant classification, even though no user data—or additional data at all—is saved with a newly classified domain, it's possible, in principle, to at least loosely associate a set of classified domains with a user based on the date the domains were classified and the date the user joined. For this reason the setting is not enabled by default.