As it introduced a new social hub, Google quickly learned that people’s most frequent e-mail contacts are not necessarily their best friends, the Associated Press reports. Rather, they could be business associates, or even lovers, and the groups don’t necessarily mix well. It’s one reason many people keep those worlds separate by using Facebook for friends and LinkedIn for professional contacts, or by keeping some people completely off either social circle despite frequent e-mails with them. Google Inc. drew privacy complaints this week when it introduced Buzz and automatically created circles of friends based on users’ most frequent contacts on Gmail. Just days later, Google responded by giving users more control over what others see about them. Google introduced Buzz on Tuesday as part of its existing Gmail service. The service includes many of the features that have turned Facebook into the Web’s top spot for fraternizing with friends and family. Like Facebook, Buzz lets Gmail users post updates about what they are doing or thinking. Gmail users can also track other people’s updates and instantly comment on them for everyone else in the social circle to see. But while Facebook requires both sides to confirm that they are friends before making that relationship public, Google automatically does so by analyzing how often they’ve communicated in the past. Those frequent contacts become part of the circle of people you follow and who follow you.