Why does tagging matter? I will explain this in terms of each of the three basic principles of digital literacy: consume, create, and connect:
From the perspective of the first principle of digital literacy, CONSUME:
Tags are "metadata" (info about info), and metadata greases the wheels of the Internet machine. Search engines will parse untagged content, but giving something a tag will make it far more easy for others to find, reference, or use.
Found a blog that you like, but you only want to read that person's views on hockey and ignore his crazy conspiracy theories? Click "hockey" in his tag cloud or list of labels and you filter out everything but that one thing.
From the perspective of the second principle of digital literacy, CREATE:
Tagging helps you make sense of your own stuff. After tagging for awhile, whether that's tagging items that come in on your Google Reader, or blog posts, or photos -- you start to see some patterns emerging. User-generated content is casual -- it isn't formally organized. But tags can magically give coherence to a mass of stuff. When I wrote a sonnet a day for a year, those poems really started to add up. What were my main topics? Very easy to see by glancing at my tag cloud.
When you tag, it shows that you are thinking about what you are producing. In other words, this is one method through which you fashion your online identity -- by what you tag and what your tags are. Tagging is a conscious activity. You've had to ask yourself, "Now, what is this about?"
From the perspective of the third principle of digital literacy, CONNECT:
The fact that you curate your content with tags shows a certain investment in the content, in the tag subjects, and in the process of contributing meaningfully to a network through which others can find and use what you share. Taggers are good citizens of Infotopia.
Tags are ways of finding people to follow within a social network. On a social bookmarking site like Diigo, if I notice certain people keep using the same set of tags that I do on their bookmarks, I am likely to pay attention to them and perhaps follow their bookmark stream. Whenever we add details to a profile page (such as interest in a book or film), we create metadata about ourselves that becomes a bridge to other people. Click on one of the media items you've listed as something you like within your Facebook profile. See how it takes you to other people.