> I'm still surprised no one has yet figured out a way to store sensitive data about personal interests and preferences on the client-side and let the client itself pull appropriate ads for the user to see.
I guess the problem is the same as with privacy techniques in general. If you ask companies to restrict their access to data, they just tell you no(1), as it might be worth a lot of money or open up new business oportunities they haven't thought about yet.
(1) This is anecdotal from projects of my colleagues in privacy research
That cuts both ways, so we trust the client (users have to, even if remote sites do not) and do not trust servers to take individual user data in the clear and use it wisely & fairly. This applies to Brave servers too. Flip the model.
When I was at Middleware2017 I saw a poster/demo about this, MoCA+: https://koreauniv.pure.elsevier.com/en/publications/demo-moc...
I guess the problem is the same as with privacy techniques in general. If you ask companies to restrict their access to data, they just tell you no(1), as it might be worth a lot of money or open up new business oportunities they haven't thought about yet.
(1) This is anecdotal from projects of my colleagues in privacy research