With the popularity of sites like del.icio.us and YouTube, tagging has become (for better or sometimes worse) a standard feature of nearly every site on the internet, and virtually everyone has a pretty fair idea what tagging is and how to use tags online. But the latest operating systems from Apple and Microsoft also have tagging built into their filesystems, meaning that the same basic tagging ideas available online are also available for the files on your hard drive. It sounds like an excellent idea in theory, but it doesn’t seem as though offline tagging is taking hold. So we’re wondering: