I've been pondering tags and tagging recently. It is popular throughout the web these days, with Flickr, Last.fm, Technorati, del.icio.us, etc all allowing us to tag things. But are all these tags actually useful?

(I'm never too hot at articulating my point, but here goes!) I myself got swept up in the tagging craze and started tagging my posts automatically using the Yahoo Content Analysis API, to produce a nice tag cloud. But what since then? I hardly ever use it to find things on my site, I either use the archive or search. My tags, to me, are pretty useless. But that raises the question, what use did I expect to get out of them? For services like Flickr and Last.fm where the content, photos and music, is not text based, tags make sense. They provide an easy way to describe the objects in text, so you can find them again. And everyone describes images and music fairly similarly, (e.g sunrise, classical).

For me tags become less useful with textual content. How I tagged something one day can change, you adopt new ways of tagging, it becomes more confused. But maybe that's an issue for me, maybe tags aren't for me, perhaps I prefer a more structured way of marking things, like favorites in folders. As Tony rightly pointed out at work, the moment you start think how you can organise tags hierachically, you've missed the point of tagging.

So in conclusion, are tags useful? I guess given the right application yes, but I want to know your thoughts. Do you tag things, and actually use the tags, or do they just sit there looking pretty but useless?

So on to my next point, tag visualisations. The obvious one is the tag cloud. The tags are ordered alphabetically, and the size and colour of a tag is larger / brighter the more it is used. It is a simple and effective way of visualising tags, but I'm sure that we can do better.

Yahoo researchers have been playing with new visualisations for tags (taglines) but I'm not sure its particularly useful in its current incarnation. It raises some questions though. How can we show tags over time? How can we cluster related tags together and show that? How can we show the actual items these tags represent? How can we display / understand the relationships between tags? Lots of questions, but no obvious useful tag visualisations out there. And this is where you can help, I've had a look, but if you have found anything you think covers the above let me know!

I could go on for ages about this, but I'll stop here and see what comments I get in. I want to get a little discussion going about this, so please, let me know your thoughts on tags and their usefulness, and any good tag visualisations that beat tag clouds in their usefulness (they must be useful.) Go!