Sorry for double toast but,
Now that I think about this this may even cause a war, due to the majority of websites being based in the states. I'm pretty damn certain this would start several riots in the gaming community and most other internet-based communities. I'll be pissed as hell if they do this.
I think this would happen if stuff.. happenned. along with the things in my above post.
Lots and lots of songs erased from youtube, the site possibly even being shut down
Just about every source of real information about the outside world being erased
Lots of angry children complaining about their research being restricted to 18yos.
I could also see lots of fandoms and groups and whatnot being barred. Bronies, Furries, Some weeaboo groups, Stuff like that.