You can compare to get newly registered domain names so it's sometimes used for Spam to target new companies - I've not noticed that so much lately though.

I suppose you could identify recent NS changes to create a list of servers/hosting that might not have been locked down or secured yet.

But on the whole I can't personally think of anything too bad.

You can also do that with certificate transparency logs though.

didn't they already doing this?

i remember getting lot a spam from different persons/agencies to develop a website for my newly bought domain.

Whatever marketeers can come up with.

I believe you have to sign an agreement to not use the domain names list for DDoS attacks, specifically against WHOIS services. Not saying that this stops anyone, but that's what they probably had in mind.