Google has a new particular search engine for probing Google Profiles. It has a better boundary than the regular Google Profiles search feature, it's included with Google Search and it shows extra links from people's profiles.
This attribute is not yet enabled in the interface, but you can look for Google Profiles by adding up &tbs=prfl:1 to a Google Search URL. Here's an pattern.
Google could use the data from user profiles to offer advanced search features like restricting profiles to people who lived in Chicago, attended Long Island University and are involved in sports.