"The approach allows measurement without disclosing who, specifically, did what with the ad."
If this is "privacy", then it appears so-called "(ad) tech" companies are attempting to redefine the term.
Question for readers: Is knowing the identity of a person a prerequisite for that person to lose (some) privacy.
Consider the dictionary definition:
Webster's: "The state of being in retirement from the company or observation of others; seclusion."
Wordnet, from the Cognitive Science Laboratory at Princeton: "the quality of being secluded from the presence or view of others [syn: {privacy}, {privateness}, {seclusion}]"
Example:
A person in a building in a large city on a busy pedestrian street draws the curtains or blinds in a window facing the street to prevent passers by from seeing in. The passers by do not know the identity of the person(s) inside.
The scare quotes around "privacy-preserving" are justified. The act of allowing measurement destroys some privacy. It is less private to let people on the street see into the building.
Allowing measurement destroys privacy. How can marketers make it easier to swallow. Using a term like "privacy-preserving" is obviously deceptive, it is sleight of hand to conceal the frog boiling. This is not Mary Poppins. You are not being given a spoon full of sugar to help the medicine go down in a delightful way. It's poison in small doses. Eventually, the frog will die.
The "frog" is the concept of your privacy. The notion of "privacy" for so-called "tech" companies is not being targeted. Even when courts ask them to share what they are doing, they evade such discovery claiming it would put them at a competitive disadvantage: they might ultimately lose money. Whereas if opening yourself up to 24/7 observation causes you to lose some advantage and ultimately to lose money, then your loss is their gain.
There are certain risky activities in life that some folks choose not to engage in. These activities can be made "safer" and even "safe enough" that many will choose to do them despite the risk. But it does not remove all the risk. There are endless examples. Skydiving, bungy jumping and so on all the way down to relatively mundane stuff. But in almost every case, there is an incentive to participate. There is a "reward" for taking the risk.
The incentives for Mozilla, "ad tech" and all those who support this nonsense "business model" based on surveillance is easily discernable. Finding an incentive for anyone using a web browser to want to participate in this "measurement" requires mental gymnastics.
And so it must be opt-out. No one would knowingly subject themselves to such needless observation.