This ruling is something we have always been concerned about from a business point of view, because ever since it became untenable to claim US companies could actually protect any personal data at all the basic legal premise on which Safe Harbor was built has been shaky. We don't know now whether it will still be sufficient to merely disclose our commercial partners in our privacy policy (which we do, by name and with an indication of what we use them for) or whether we need some sort of more active consent.
I haven't had chance to speak to our lawyer yet, but I'm expecting him to tell us something along the lines of: the law now requires us to add yet another prominent notice at the conclusion of a sale. On top of all the consumer protection rubbish from the recent EU changes there -- which again were well-intentioned but actually impose silly things that help neither us nor our customers -- the number of such notices we need by law is making our sales pages almost comical now. I can't believe all these notices really help to protect anyone from much of anything in practice, and anyone reading this on HN probably knows what effect compliance has on conversions.
The second to worst possible outcome is probably that we are now required to seek active consent from our existing customers before continuing to use things like US-based payment services. The worst is that it actually becomes illegal to use those services at all, though I don't think that is going to happen.
It's sad, because from a personal point of view this mess is long overdue for being cleaned up. But the authorities are so clumsy about handling these issues that a lot of the time they just hurt small businesses and legitimate international trade.
The big issue is the fact that we have become accustomed to being relived of both the choice and the information about which choices thats been made for us. Which of course makes us a bit lazy since it's hard to make informed choices which probably is going to make a system like the one you described a hassle to implement but id say it's worth it to bring back at least a small resemblance of choice and control of your own information.