"A Google Profile is simply how you represent yourself on Google products — it lets you tell others a bit more about who you are and what you're all about. You control what goes into your Google Profile, sharing as much (or as little) as you'd like."
Profiles are public and contain basic information about yourself: a nickname (the real name is displayed only to your contacts), your occupation, your location, a list of links, a photo and a short description. They are embedded as iframes in pages that showcase user-generated content (personalized maps, shared bookmarks).
A side-effect of the public availability of your profile is that people can find it. "Can people do a Google search for my name and find this profile? It depends. If you put your full name in the Nickname field, pages on which your profile appears may be returned as results by Google." You can already find more than 100 profiles attached to Google Maps pages. Maybe Google will even create a directory for profiles and start to suggest friends based on personal descriptions, location and activity streams.Google, Google Profiles, Online Identity