[yakult]

what percentage of FF users on the planet do you expect could read a paper on differential privacy and actually verify those points, while understanding all the ifs and gotchas, and be able to tell if any of the arguments are wrong? What percentage of that elite group would actually be willing to devote the time and energy, for free, for every one of the thousands of softwares they use?

[NabenHarb]

Not many, certainly. Which is perhaps why it's better for this to be implemented (since differential privacy is a known, rigorous definition for privacy), rather than to leave it up to the larger majority of users who (by your implication) don't understand it and won't be bothered to understand it.

[yakult]

...or you could just scrap the whole idea and not bother with it.

This is true for the user, too. If the only viable choices are 'verify claims at great cost and no gain every few months', or 'use some other privacy-respecting browser', I am going to recommend the second.