Re: Not my field of expertise
"how do you remember to forget them on a restore?"
Ironically, you'll probably need to "remember" them in a "forget" data set. Google will have to "remember" them in a "forget" algorithm, too, so that search results don't show whatever it is that's supposed to be "forgotten". And don't even get started on www.archive.org [it's a GREAT resource for 'forgotten' data files and web pages that you might want to research, but are no longer available].
I guess www.archive.org could just make it impossible for EU people to access it... or "remember" to "apply the 'forget filters'" if you have an EU IP address or something.
I like the idea of GDPR in principle, but I think the actual mechanics of it will have too many unintended consequences [like for backups].