Google is seriously concerned about duplicate content and various site issues. Few months back, Google explained multiple pros and cons of duplicacy in the content and the related issues showing their concern over it.
According to the Google's Webmaster blog, last month a talk was given at the Search Engine Strategies San Jose conference on Duplicate Content and Multiple Site Issues. But for those who could not make it to that conference, Google has reproduced the talk on the Google Webmaster Central YouTube Channel.
Below is the short video reproduced in this regard at the Search Engine Strategies San Jose conference.