Google often penalizes identical content across multiple websites—however, the Google algorithm is intelligent and recognizes whether the elements in the header and footer are consistent or whether entire text passages are accessible twice under different URLs. The question of how Google handles blog article overview pages is particularly interesting.
On the Google Webmaster Help YouTube channel, Matt Cutts offers a brief explanation: The safest and most convenient way to include articles on overview pages is through the mandatory "Read More" link in the form of teasers. Incidentally, the YouTube channel features over 500 videos from Google. Watching them is highly recommended.