You can verify this for yourself by visiting the provided URL
http://bit.ly/iT6p3n or directly at
https://ssl.gstatic.com/s2/sitemaps/...es-sitemap.xml what you will see when you visit that link is a xml file listing all of the various profiles grouping. Just copy one of the links place it into your browser and you will then be taken to another site with the links to the actual profiles copy any of them into your browser an you will be a bit surprised.
Why should you care about this you might ask? Easy its only a matter of time before some creates a script to harvest all of the following:
Usernames, first-name, last-name
GPS co-ordinates of places you have lived, if you filled that out
Personal photos
For that you should be a bit concern but maybe Google is not. According to
https://twitter.com/#!/tomokas he stated that he mentioned this to Google back in 2008 and only got an auto response email.