

And while I understand that not everything is private, we have laws against gathering public data about people but only if you’re just one person.
That’s not why. The reason is nothing you wrote about fits the legal definition of stalking. A typical legal definition
A person commits the crime of stalking when the person either:
- engages in a course of conduct or repeatedly commits acts toward another person, including following the person without proper authority, under circumstances which demonstrate either an intent to place such other person in reasonable fear of bodily injury or to cause substantial emotional distress to such other person; or
- engages in a course of conduct or repeatedly communicates to another person under circumstances which demonstrate or communicate either an intent to place such other person in reasonable fear of bodily injury or to cause substantial emotional distress to such other person.
An element of the definition (circumstance) is sorely missing in your claims.
Stalking has less to do with information & more to do with (legal definition of) harassment. Simply gathering public data about someone isn’t a crime. Expectations of privacy in public are nonexistent. Your premise is dubious.
I don’t know, man. I assume they have information they may find in a phonebook; data I voluntarily gave social media & networking such as my school or employment, demographics, relations, peers, & whatever they can glean from peers; my shopping preferences; rough geolocation from my IP address; my ISP, OS, web browser, content I’ve browsed. None of this information is particularly valuable to me. It would take incredible effort for me to code & host a search engine or social media site or the various other free web applications I use. I value those way more than my junk data that is worthless to me, so the trade-off is obvious.
The government has access to much more sensitive information about me: social security; government issued licenses & registrations; birth, education, tax, property, police, medical, telecommunication, financial records. Only the law & procedure prevents it from abusing that access.
Without online data brokers, anyone could gather much of the same, less sensitive information about me though plain observation, public surveillance, or interviews: only time & effort discourages them. Seems like a lack of perspective.