In an episode of Linux Unplugged they talk about Richard Stallman's proposed solutions to the problem of companies spying on people and then using the data in dubious ways. After a lot of meandering the actual discussion is about an hour into the show.
So what's the solution to this? Cambridge Analytica isn't the first company to use data in sketchy ways and it won't be the last. I also don't really agree with Stallman that legislation is the answer, since here in the UK the data protection act has existed for decades and even though there are many violations of it it's largely ignored.
For example, the data protection act says that data collected about people is supposed to be used by the "data controller" for a specified purpose, not for purposes different from the one for which the data was originally supplied, and also that people should be able to obtain copies of their data without unreasonable delay. When you think of the world of advertising companies and data brokers and so on it's easy to see that these basic rules are being broken routinely. Data supplied for one reason ends up being used for entirely other purposes. Maybe somewhere in the terms of service there are buried descriptions of what happens to personal data, but realisticly nobody except lawyers reads those documents and the problem boils down to what constitutes meaningful education and consent.
Things that have been tried and which we know don't work are:
In the Linux Unplugged episode FreedomBox is mentioned as a possible solution to the data ownership and privacy problem. I like this idea, but I think there's also another possibility which is non-corporate community management of systems - especially social networks. That is, the kind of federated model which exists already on the Open Web. To some extent the work involved with storing and managing communications data can be collectivised within an affinity group so that each user of the system doesn't have to take on the whole responsibility by themselves.
A couple of years ago it would have been easy to dismiss the federated model as something old-fashioned, perhaps resembling the bulletin board era before the internet, but now there are thousands of Mastodon installs and what appears to be very active communities around them who are not just the previous demographic of hardcore Stallmanites. What exists today is a pretty substantial proof of concept for an exit strategy from the current data dilemmas. It's not that today's fediverse is ultra private - far from it - but it's conceivable that better privacy features could be added.
What I think organisations such as FSF, EFF and ORG need to be doing is getting behind projects like FreedomBox and promoting them and showing people how to install and maintain them. If data is increasingly managed in a non-corporate way and perhaps also at a more municipal level then at least when it comes to devising legislation the pro-privacy side of things will be in a much stronger bargaining position.