TIL about it after reading this post. It seems to have started around 17/April
From the article:
a login barrier for reading does not really stop AI scrapers because bots can be equipped with accounts within a few minutes. Instead, many suspect that Amazon’s main aim is to increase the number of registered users. After all, those who are logged in can be tracked better – and can be provided with more targeted recommendations and advertising.
Are there open source alternatives to it?



I stopped using IMDB ages ago when they started serving their ads through the same domain they host all their other images on, so blocking ads broke the site entirely.
I left those ads blocked though, and just stopped using IMDB. Looks like I made the right choice.