This is a fairly major change, and will have some fairly significant impacts on the AdTech industry. I'd go as far as saying this was the first really meaningful fallout from the CA scandal.

I'd hazard a guess that not many ordinary users are even aware that retailers can upload their email addresses into Facebook and create targeting segments from them.

As to what these changes do to the AdTech industry is anyone's guess. 'Onboarding' email addresses is basically LiveRamp's business model.