If I had a nickel for every "secure" app that handled sensitive user data and then subsequently leaked that data this year...
I'd only have 20 cents, which I guess is good. But I'm sure there's more I'm forgetting.
Related:
[1] https://news.ycombinator.com/item?id=44684373
For this specific movement, venturing outside Facebook Messenger is an important cue.
and these are just the ones we know about