US collecting detailed data on regular citizens who travel

From the Washington Post:

The U.S. government is collecting electronic records on the travel habits of millions of Americans who fly, drive or take cruises abroad, retaining data on the persons with whom they travel or plan to stay, the personal items they carry during their journeys, and even the books that travelers have carried, according to documents obtained by a group of civil liberties advocates and statements by government officials.
Officials yesterday defended the retention of highly personal data on travelers not involved in or linked to any violations of the law. But civil liberties advocates have alleged that the type of information preserved by the department raises alarms about the government’s ability to intrude into the lives of ordinary people