(From an interview of Jared Diamond, author of "Collapse: How Societies Choose to Fail or Succeed")
Sierra: You say in your book that a society's core values often spell its ruin.
Diamond: Yes, the most difficult values to jettison are those that have helped you in the past. You're inclined to cling to them. The Greenland Norse had a problem maintaining their European dairying society, a week's ship journey from Europe. As European Christians, they also despised the Inuit as pagans. Now, they could have survived if they had worked out the same trading relations with the Inuit that the Danes did in the 1700s, but the Norse held values that would not allow them to deal with these pagans and certainly would not let them eat fish and hunt ringed seals the way these pagans did. So here is a case where the values that sustained them for 450 years ultimately killed them. The United States faces similar agonizing reappraisals today.
Read the whole interview at http://www.sierraclub.org/sierra/200505/interview.asp
or better yet read the book.