One day after its launch, privacy concerns have been raised about Google's new Gmail-based social-networking tool, Buzz.At issue is a feature that compiles a list of the Gmail contacts who users most frequently e-mail or chat with. Buzz automatically starts following these people and makes the list public, meaning strangers can see who Buzz users have been in contact with.The issue was noted by the Silicon Alley Insider on Wednesday. "Imagine ... a wife discovering that her husband emails and chats with an old girlfriend," the Web site said. "Imagine a boss discovers a subordinate emails with executives at a competitor."There are some mitigating factors, however. Buzz only shares information about other people who are using Buzz and have set up public profiles in Google. So currently, most Gmail users are not publicly listed by the service. Users can also "unfollow" people who they don't want to be linked to. And while Buzz requires users to set up a public profile before they can post messages, it does give them an option to hide who they are following and who is following them. However, the default setting is to make the information public, and only users who click on an "edit" tab can see the choice to opt out. That means many people who start using Buzz may be publicly linked to other users without realizing it.Reached Wednesday afternoon, a Google spokesman had no immediate comment.Google introduced Buzz as an alternative to popular sites such as Facebook and Twitter, which are increasingly being used to navigate the Web.