Gmail's spam filtering is certainly not run without consent or knowledge, unless you think I should be reviewing each piece of spam individually. It operates with the consent of spammers, but that hardly matters.
Changes to Gmail's spam filtering algorithms, however, do happen without your consent or knowledge. Similar to how changes to the algorithm governing FB's News Feed happen without your consent or knowledge, but you know that it exists. Like your spam folder, you can tab to "Most Recent" to see what you are missing.
