I'm a publisher for >10 years. At first I used the policing services, but I stopped worrying about torrent sites and other low-grade pirates when it was clear that A) most readers don't use them B) site operators are located overseas and don't give a FF about U.S. C&Ds and C) I have better things to do with my time.
As for pirates on Amazon itself, or other major marketplaces: That's a different story. I have a registered trademark on Amazon Brand Registry and do use it to find bogus copies and copyright violations (usually in the marketing copy or cover images) to get them removed, with about 60 or 70% success.
She doesn't care if people pirate her books, she just cares that Amazon might take her books down from Kindle Unlimited if they discover a pirated copy online like they've done for many other authors.
Almost all of her income is from KU, not book sales, so it would crater her revenue.
It's MUSO. $7/mo per book or $70/month for your whole catalog, so I guess once you get 10 books out there the price flattens out.
Only reason I didn't mention it by name in my earlier comment is I forgot what it was called, I had to ask her.
And to be clear I don't think MUSO is a bad company or anything, just that it's insane to me that authors have to feel like they have to get this service just to maybe hopefully keep their books on KU (or maybe hopefully facilitate getting them back on if they do get removed).
As for pirates on Amazon itself, or other major marketplaces: That's a different story. I have a registered trademark on Amazon Brand Registry and do use it to find bogus copies and copyright violations (usually in the marketing copy or cover images) to get them removed, with about 60 or 70% success.