[aylmao]

USPS has rules about what can and cannot be sent, and it seems like they can open your mail if they suspect it contains something illegal [1].

[1]: https://gotogreatpanes.com/blog/2014/02/03/can-usps-open-my-...

[jeffdavis]

That seems pretty different from what Facebook is doing. Facebook is pretty obviously curating content, but USPS is not.

[ntsplnkv2]

That's because people can ship dangerous things in the mail. The post office isn't controlling information sent in the mail.

There's a big difference between opening something up (many times needing a warrant, as your link says) because it may contain a weapon or biological agent or invasive seeds of a plant species, vs controlling what information is passed or not.