What advantages obtain from direct tagging, whether manually or by widget, vice using the WP category?

This question comes from James Joyner.

This is a widely-held debate, so I’ll provide my own opinion. ;-) As far as Technorati, and perhaps Google Blog Search is concerned, WordPress categories and tags are one and the same. However, there is a deeper semantic difference that affects users as well as information architecture. In fact, I think we’re on the brink of seeing more tagging-related services that treat tagging differently than categories. WordPress 2.2, for instance, will have tagging in the core in addition to categories.

From a birds eye view, I generally describe categories as filing cabinets. Posts go in different filing cabinets based on politics, sports, web development, local restaurant reviews, etc. However, tagging is much more granular. For instance, there might be a local restaurant that the Baltimore Ravens frequent after practices. Tagging, semantically, allows you to label that post in a more granular way: “nfl ravens restaurant microbrewery”.

This takes another level when you get outside of posting – and this is more of an abstract philisophical argument. Maybe the future holds tagging of blogroll links (There’s already XFN, but I digress), or tagging of other people’s content (think del.icio.us). What if there were a way to use internet-wide tagging to essentially fingerprint someone’s tendencies?

Conversation can be linear in a standard blog format. Post 1 with comments about post 1, followed by Post 2 with comments about Post 2. Hyperlinking has always created a way to de-linearize conversation but it is only effective to a degree. If you think about it, tagging reflects the actual human thought process and behavior. How often do humans only think and talk about a single topic – yet, on blogs, thats exactly what happens. One post, with comments. Second post, with comments.

The second part of the question deals with actual implementation – widgets, tag clouds, etc. To me, this is secondary to the actual tags themselves. While Technorati does respect WP categories as tags, it also handles tags themselves, if they exist, as a separate entity as well. In the end, we’re going to see many implementations, but taxonomy as a whole poses a huge windfall to bloggers who choose to use them.