Can the U.S. government legally monitor private communications? If so, given the U.S.'s significant protection of privacy rights, what government cannot?

Wikimedia Foundation v. NSA/CSS is the most important case ever regarding whether a government can monitor private communications. This case's discussion could not be any more timely for public affairs purposes. Given continuing terrorist attacks and concomitant calls for private industries, such as Wikimedia Foundation, to do more to stop the spread of violence and rhetoric on the Internet, there has never been a more important time to consider what limits should be placed on government's access to personal data in the quest to prevent terrorism. Here, the district court referred to the plaintiffs' injuries from NSA upstream surveillance as speculative, denying them Article III standing. The Fourth Circuit reinstated Wikimedia Foundation as a plaintiff, finding sufficient allegations for it to survive a facial challenge to Article III standing based on the Wikimedia Allegation. However, the other plaintiffs, relying on the Dragnet Allegation, were properly dismissed based on lacking standing. Until more details of upstream surveillance become public, suing under a dragnet theory should prove difficult. In fact, lobbying the legislative and executive branches to enact changes could be more effective and efficient than relying on the courts.