[webstersII]

"Some level of government owns library computers. "

That's correct. But the states owns the libraries, not the Federal Gov't. Same is true of computers on college campuses.

"The same applies for the computers at a local Kinko's or cyber cafe if they are operated in a locality that carries so-called decency statutes on its books. "

These are private businesses and are not owned by any gov't. The decency statutes are state and local laws, not federal laws, so that doesn't make them automatically available at the federal level.

[.cnI redruM]

True. In that case, state and local authorities, rather than the Feds, could violate your privacy at will on those machines. It's case of whomever is paying the piper calling the tune.