The White House and the Centers for Disease Control and Prevention are asking Facebook, Google and other tech giants to give them greater access to Americans’ smartphone location data. The move has set off alarm bells among privacy advocates who fear what the government may do with users’ data. Some sources stressed that the effort would be anonymized and that government would not have access to specific individuals’ locations. Similar and more aggressive surveillance practices have already been put to use in China, South Korea and Israel. Facebook already provides health researchers and nongovernmental organizations with data to help disease prevention efforts.