In context: Google's acquisition of Fitbit is being probed by the US Department of Justice (DOJ) over privacy fears. Both the DOJ and Federal Trade Commission (FTC) had sought authority to investigate the deal, but the former agency was put in charge of the review because it is already examining Google's anti-competitive practices.

As reported by The New York Post, both agencies were concerned over the sensitive health data that Google would have access to as a result of the purchase. Privacy advocacy groups such as the Center for Digital Democracy, Public Citizen, and Consumer Action have already urged the government to block the deal for the same reasons.

"We write to urge the Federal Trade Commission to block Google's proposed acquisition of Fitbit. If this acquisition is approved, Google will further consolidate its monopoly power over Internet-based services. It will increase its already massive store of consumer data, including highly sensitive health and location information," the watchdogs wrote in a letter.

All large mergers must file proposals with both the FTC and DOJ, though only one agency reviews a merger. While most Google deals had been reviewed by the FTC, the DOJ's current investigation of the company meant it was granted the Fitbit probe.

"The DOJ's handling of Fitbit will give an early read on the Google investigation," a DC source said.

SEC filings last month revealed that there had been a bidding war between Facebook and Google for Fitbit, with the latter winning by only a small margin. Considering the social network's notorious reputation for user privacy, it's likely the current outcry would have been even larger had Facebook won.