But wouldn't the "canary" idea be more useful if the email was changed frequently? Suppose a cron job updated the email address every day to include a few non-obvious characters encoding the current date so that the spam you get tells you when that row was copied from your database.
To me it makes sense to keep good records of security events so if I were to get this "signal" I'd make sure the details were captured and the appropriate people informed. Then I'd double check the obvious things like who logged into the database server that day, who had access to backups, who may have worked on database code in that time, when that code was last (or ever) audited and so on.
