I didn't see the list, but did it by any chance contain the logos of the online stores? If it did, the DMCA notices make sense.
The claims are probably from the malware perpetrators as a way to censor discussion and keep the gravy train rolling. It's possible also that the embarrassed commerce sites would file a DMCA claim to keep the public in the dark about how insecure their sites are/were.
As long as you're okay being found guilty of perjury by a US court, or have no plans to enter a US jurisdiction in the near future, you can get any content you want taken down from any site that's required to follow the DMCA.
Service providers have a choice:
a) follow the DMCA takedown process and be shielded from all liability, whether or not the claim has actual merit
b) evaluate each takedown notice to decide if the material falls within the scope of copyright, ignore takedowns where in the service provider's opinion the material is outside the scope of copyright, and should it go to court, be forced to defend that position on its merits instead of having an automatic liability shield
What sensible service provider is going to choose option b?
This is true, but totally irrelevant as it misses the point of the question.
It's smarter (under the seriously f'ed up DCMA system) to pull it down and wait for a counter notice, at which point they put it back up, and they aren't responsible any more — the person filing the counter notice is responsible because a false counter claim counts as perjury.
At that point, the original issuer of the takedown notice can sue.
Of course, it almost never gets that far when the takedown notices are spurious, as in this case. That's what makes the DMCA such a bad idea — it's a perfect tool for censorship.
I don't think it is that simple. Yes, you may claim a copyright on whole compilation. But you could as well claim a copyright on some parts within that compilation. Since the compilation is a single document, claiming copyright on some part of it would also be sufficient for a takedown.