According to website del.icio.us, "Folders were the old way to organize your bookmarks. They were great if you only had a few bookmarks and a few folders, but as your collection grew, it became harder and harder to decide what goes where. Delicious has a new and better way: tags."
Tags were also popularized by Flickr - the photo sharing website - as a way in which to categorize photos - who's in them, when they were taken, where they were taken, by season, holiday, event type, etc. -… Continue