I think the parent comment is pointing out that the government is supposed to be prohibited from collecting information unless it needs to (e.g. reasonable susp

I think the parent comment is pointing out that the government is supposed to be prohibited from collecting information unless it needs to (e.g. reasonable suspicion), no matter if it's public or not. Specifically, in the U.S., the Supreme Court confirmed that public data can still be protected by a warrant if used to compose a "mosaic" of something within a person's reasonable expectation of privacy. https://en.wikipedia.org/wiki/United_States_v._Jones https://en.wikipedia.org/wiki/United_States_v._Jones https://en.wikipedia.org/wiki/Carpenter_v._United_States https://en.wikipedia.org/wiki/Carpenter_v._United_States So, could a private company follow you around and read every tweet you post publicly? Yes. Could a government do the same without a warrant (or even ask the company to give the information to them)? No. The restriction is on the government, not the data. I guess in Europe, now with the GDPR, this restriction also falls on companies, too.