There are currently over one billion messages posted and archived on Google Groups. People will very often use all or part of their real names when posting messages in these forums. This provides a great opportunity for people searches.
I recently found posts on these forums from a past college friend by doing some simple searches. You can do a general search for an individual like John Doe, which will search for any mention of the person in any of the messages. To weed down larger results you may want to try “John Doe” in quotation marks to find an exact string match or a search for just Doe or J. Doe for more general searching.
In addition, you can search specifically for authors of posts. For instance, author:John Doe or author:J. Doe or even author:Doe will search for posts where these names appear as an author of the message. Make sure there are no spaces between the colon after author and the beginning of the name you are searching for. Spaces should be left between first and last names in the people search.
You can try your own people searches here at Google Groups.