Tom Coates has a great post over at Plasticbag that deals with the difference between del.icio.us-style tagging (filing) vs. Flickr-style tagging (annotative). This overly long excerpt lays it out (emphasis mine, urls redacted):

Matt Webb and I did a fair amount of work around tagging with a project called Phonetags that I never get time to properly write up. As we were working on it, we came to realise that each of us had a radically different understanding of what a tag was. Matt’s concept was quite close to the way tagging is used in del.icio.us – with an individual the only person who could tag their stuff and with an understanding that the act of tagging was kind of an act of filing. My understanding was heavily influenced by Flickr’s approach – which I think is radically different – you can tag other people’s photos for a start, and you’re clearly challenged to tag up a photo with any words that make sense to you. It’s less of a filing model than an annotative one.

When I came to use del.icio.us I approached tagging in the way that made sense to me from Flickr. So any and all links were covered with loads of keywords with no thought for how they ought to clump together. I just tried to describe what the link was about in some way. Joshua and I had a bit of an argument about the way I was using it, actually. The browsing interface didn’t really suit an approach that had an enormous number of orphaned tags. You can get a sense of how out of control it all got with this visualisation of my tags. At the end of the argument I said to Joshua that it was almost like he was treating tags as folders. And he replied, exasperated, that this was exactly what they were. It was just that now an object could exist comfortably in a number of folders so you didn’t have to enforce an arbitrary heirarchy on your filing…

So two radically different forms of tagging that really share very little in common with one another – which leads to the question, is there room for two different paradigms here (at least) or will there be some refactoring and adaptation that moves us towards one or other model?

Then, by looking at how people are tagging his weblog Coates proposes a hypothesis: “the shift from people using blogs to blog [as tags for Plasticbag] represents the increasing dominance of a Flickr-style paradigm of tagging… It is my conjecture, therefore, that the folder metaphor is losing ground and the keyword one is currently assuming dominance.”

What do you think? I suspect people are mixing methods already–using some folder-type tags (e.g. toread) along with other annotative ones.

The whole post is well worth the read–for the graphs and the novel thinking about tagging (finally!).