@mcc Hmm. Can't find the list.

In any case, one of the unfortunate side-effects of the way privacy is guaranteed in the system, is by having larger amounts of submissions. The more submissions, the more noise can be added and the better individual privacy.

This is the reason for an opt-out model. Now I realize if your stance is 'ads are bad and should go away', that is not a convincing argument. But it's still relevant :-).