Copyright question

In browsing many books I have noticed many that capture people’s faces from all type of places (i.e events, regions, countries) and it is my assumption that a model release was not signed in all cases.

My question then is: If I want to publish a book (make it public) do I have any obligation to have any identifiable person bind with a model release, If it is my intention to make the book available to others.

Thank you in advance!! :-)

Here are the rules for the US: http://www.krages.com/phoright.htm