if I want to opt out from your information-gathering program I have to install something on my computer Actually I think this is the preferred approach. Obvio

if I want to opt out from your information-gathering program I have to install something on my computer Actually I think this is the preferred approach. Obviously an opt-in service (where you have to agree to web analytics) is a UX nightmare and a non starter. We can't expect that of them. So that really only leaves a cookie; which is easy to delete or lose accidentally turning on analytics again. A browser plugin is best because: a) people can see & audit what code is being run b) there is positive assurance of the opt out c) you don't accidentally lose the opt out (and thus Google avoids the eventual "angry blog post" associated with that :P)