[alfiedotwtf]

> Where to draw the line?

That line is called the Third Party Doctrine:

https://en.wikipedia.org/wiki/Third-party_doctrine

"The third-party doctrine is a United States legal doctrine that holds that people who voluntarily give information to third parties—such as banks, phone companies, internet service providers (ISPs), and e-mail servers—have "no reasonable expectation of privacy" in that information. A lack of privacy protection allows the United States government to obtain information from third parties without a legal warrant and without otherwise complying with the Fourth Amendment prohibition against search and seizure without probable cause and a judicial search warrant"

... but if you really want true privacy:

"If you want to keep a secret, you must also hide it from yourself" -- George Orwell, 1984