I spent a couple of decades in big-tech, and of-that did adtech for about 5yrs - we captured, aggregated, cooked out activity streams from billions of toolbar, browser, and beacon events per day, for real-time, long and short-term user profiles for around a couple of hundred million people - primarily for feeding the ad-exchange behavioral targeted ads. Back then about 80% of the active internet users. This was a huge business even back then - billions.

Since then the world and his wife have captured data and inserted telemetry beacons everywhere. Consider how many services you use that are today subsidized by “anonymized” selling/trading/sharing/merging user event streams - the TV your watching, your cellphone provider selling user behaviour data, even your ISP is selling your DNS lookups - they’re all at it now. Worse, mobile has made it much easier to install platform frameworks that offer developer features in return for data-collection such as location, user profile etc.

I don’t think it’s overblown - that “anonymity” isn’t that anonymous when you add enough dimensions - you just haven’t seen how massive the data broker business is.