I have used tagging through my Delicious page, but have not yet seen it being used in libraries. I can certainly see where that would be useful though. We all know there are rules that govern how libraries are organized, but if patrons were able to do it, wouldn't it make sense that it would be a better system? After all, they are the ones that are using the tags and organization. The only problem of course is that the way I would tag an item may not be the way you would. And now we have chaos.