Even more important than that for me (possibly for you too) is that you make sure that none of these pages make it into googles index. The duplication of conte

Even more important than that for me (possibly for you too) is that you make sure that none of these pages make it into googles index. The duplication of content (potentially sending the original pages down in search ranks) and the fact that you are polluting the organic search results for the sites you mirror could be a big issue for the owners of the pages.