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.

> at one extreme you have people who can audit software they use and verify that it actually does what it says

Unless the software sends data off to the cloud or a sever somewhere. You can't audit what happens there.