Metadata is a great feature for easy retrieval of files in any document management system, not only in SharePoint. But sometimes people forget that in some cases, the metadata is stored in the file itself, not only in the repository.
This can lead to painful situations, as Microsoft experienced recently with their new “I’m a PC” ads.
If you are storing Office files on SharePoint, the same thing happens: metadata such as SharePoint columns or content type info gets stored in the file itself.
If you are using Office 2007, you can use the Inspect Document function to search for hidden metadata, and strip this from the document. This screencast shows you how SharePoint metadata remains in a Word document, and how you can use Inspect Document to remove the metadata.