Earlier quoted context omitted.
Oh boy. It's NOT about whether something's "public" or not: It's about someone "connecting the dots" between ALL your public activities. Someone following you OUTSIDE their "space" that you visited and then invading your other spaces. People don't usually want to mix their social circles. e.g. nobody likes a snoopy overprotective parent following their [teen] kids around wherever the children go with their friends. N…
Someone would only be able to connect the dots based on what you publicly put out there. If you don't put anything out, there's nothing to connect the dots, unless you buy some sort of dark web leaked dataset. None of your analogies are comparable to online public information because you decide what to put out online, and I never said anything about legality so not sure why you bring that up.
Customers of such datasets: banks, insurance companies, HR companies, marketing firms, governments, etc.