The problem is that large-scale use of the Internet for social networks and for organizing meetings in real life is fundamentally incompatible with privacy. It works for small, tight-knit insular groups, but as soon as you expand the scope of the network to include acquaintances and friends of friends you'll eventually find a connection to someone who cares less about privacy than about making a buck.

If we had a sort of "federated" system we'd still have this problem because you might always find yourself federated with someone who just wants to sell the information.

It's a cultural problem within this hyper-aggressive version of Capitalism that we've adopted, that even data about people has value. Until we decide as a culture that this kind of data sale or data use is shameful and unacceptable we'll be in this situation no matter what technical solution we adopt.

Users who want to be private and are willing to pay extra for it are necessarily highly valuable for data brokers and advertisers. So incentives always push towards betraying them eventually I think.

This is a multi-axis problem.

On one spectrum, you have privacy -- at one extreme, the most private of people don't even use social apps, they are traditionally private people. At the other extreme, you have the highest consumers of apps -- the people who demand sharing the most.

On the other spectrum, you have technical acuity -- at one extreme you have people who can audit software they use and verify that it actually does what it says -- at the other extreme, you have people who have no clue and will believe whatever is convincing.

Given this, the market for "app that enables sharing, but has privacy controls, and is verifiably so" is a tiny circle somewhere in the middle of this grid.

Not privacy-focused, but OKCupid itself fit many of your requirements when it first came out. It wasn't aggressively seeking hyper growth and barely marketed outside of existing SparkNotes and SparkMatch users. It was just a few math nerds at Harvard that wanted to model human romantic compatibility by categorizing you into a shareable cutely named personality type, and they bolted on crowd-sourced questions to see if whatever they hadn't thought of themselves might be relevant.

Ten years later, the social media revolution is in full swing, the relatively small service they built that had catered mostly to nerds was suddenly lucrative, and they sell to Match Group and this happens.

To be entirely fair to these guys, I don't think they came into it intending to sell out as their long-term goal. But four guys who got into data analytics in college also didn't find themselves as their mid-30s approached particularly wanting to run a dating service for the rest of their lives, either.

Whatever happened to FetLife? If any dating service had to be privacy-focused, that was it.

> I have long wondered about the market size for privacy-focused apps.

The real problem is how to trust that a "privacy-focused" app is actually privacy-focused. You certainly can't take the publisher's word for it.

The only safe stance is to withhold as much personal information from as much software and services as possible.