Yes, I'm aware of this (and thankfully have never been stupid enough to entrust my address book to any such service), but what I'm really looking forward to is how Facebook and their ilk will be dealing with shadow profiles in relation with the GDPR.
Since I'm not a member of their service there's no valid reason for them to maintain personally identifiable data about me. Let alone that they never asked for my permission and that I never, ever consented to their gobling up of my data and that of other non-members.
At least according to my understanding this is a very clear violation of the GDPR, which - if the courts agree - could cost them dearly.
I wonder how Facebook intends to deal with that. If I interprete the directive correctly they are obliged to delete all such data since storing, mainting and proecssing it clearly violates the law.
Interesting times...
