Adam Lasnik wrote a few tips about the handling of duplicate content in Webmaster Centrals Googleblog. Google is recommending to avoid duplicate content on a page through a consistent directorystructure and 301-redirects when files are rearranged. For different country-versions of a homepage you should use the corresponding domains instead of subfolders as far as it is possible. If there is content that is offered for redistribution (RSS-feeds), a link to the original text should always be included. This way Google seems to have an easier time detecting the source-version of a text. If pages are copied without consent, Lasnik is advising to fill out a DMCA-request.