Because Signal tried to show people exactly how much data F*c*book has about them. The Instagram ads Facebook won't show you
We created a multi-variant targeted ad designed to show you the personal data that Facebook collects about you and sells access to. The ad would simply display some of the information collected about the viewer which the advertising platform uses. Facebook was not into that idea.
Here's a sample of the ads that users would see. But F*c*book didn't think it was a good idea for people to know how much F*c*book knows about them.
Facebook’s own tools have the potential to divulge what is otherwise unseen. It’s already possible to catch fragments of these truths in the ads you’re shown; they are glimmers that reflect the world of a surveilling stranger who knows you. We wanted to use those same tools to directly highlight how most technology works. We wanted to buy some Instagram ads. [SNIP]
Facebook is more than willing to sell visibility into people’s lives, unless it’s to tell people about how their data is being used. Being transparent about how ads use people’s data is apparently enough to get banned; in Facebook’s world, the only acceptable usage is to hide what you’re doing from your audience.
No one should be using F*c*book for anything. Certainly no one who values free speech and opposes censorship. (And yes, I know this blog is hosted by Google...) Firefox, as a browser, with the Facebook Container, together with uBlock Origin and Privacy Badger screens out all attempts by F*c*book to track what I do. (Hat tip to Instapundit)