If you are posting something on the web, please display the posting date or last updated date with your posting — please, please, please. Google should be able to show the date the posting first appeared in their index but that doesn’t prevent a user from reusing content on a different URL. How would Google know if the content had changed or just the banners around the content. It is up to publishers to include the relevant meta data.
http://twitter.com/billwesterman/status/11106822559
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