I see no other way of capturing real photography of people, unless they are truly unaware that they are being photographed. It seems that as soon as someone knows they are being photographed they strike a pose, no matter how much one asks them to please to act natural.
This following articles explain the process of shooting these types of photographs, along with results of such style of photography:
Part II of the article introduced me to a very talented real-life photographer Garry Winogrand, who’s speed and agility in taking photographs are very impressive. Here is the direct link to his documentary:
Here is a nice article discussing photography of strangers on Flickr: