[avian]

I've seen these dark patterns justified by "UX experts" like so:

1) Make a A/B test with an annoying pop-up sign-up box and an ordinary unobtrusive one.

2) Data shows that more people sign up using the pop-up.

3) Obviously people want to sign up, but can't find the unobtrusive box.

4) Hence, the pop-up design helps people achieve their goal (of signing up) better and is therefore more user friendly.