I understood that the benefit of this to ISPs was to offer targeted, individual marketing. So I doubt they are selling by bloc/demographic, I suspect it's somet

I understood that the benefit of this to ISPs was to offer targeted, individual marketing. So I doubt they are selling by bloc/demographic, I suspect it's something more like Adwords. User data may be anonymized by name but it doesn't take that many data points of e.g. someone's search history to identify them. It's unclear to me what, exactly, you will be able to purchase, but it wouldn't surprise me if they can narrow a larger data buy down to a few individuals with high probability. About a decade ago now there was a leak of anonymized google search history and some researchers successfully tracked down several individuals. Google/FB/etc get away with it because you don't have to use their services, although things like the supercookie are highly specious. If you want to use any online resources you are going through an ISP. I, too, think the opt-in model is not unreasonable, but you know it will be buried in the most obtuse, double-negative-filled language their lawyers can contrive.