Launched in February 2010, Buzz initially used its Gmail customers' email contact lists to create social networks of Buzz contacts that the rest of the world could see, which led to an uproar.
Google quickly changed the settings so that contacts were kept private by default.
The FTC charged that Google was deceptive in leading its Gmail customers to believe that they could decline to participate in Buzz. Those who declined were still included in certain Buzz features.
"For users who joined the Buzz network, the controls for limiting the sharing of their personal information were confusing and difficult to find," the FTC said in a statement.
Efforts to reach Google for comment were not immediately successful.