Once you’ve played with tags at Flickr and del.icio.us for a while you’ll find you expect everything to work that way. Tags are very persuasive. Two really obvious applications for tags: Apple’s iTunes and iPhoto. Adding keywords to iPhoto pictures is such a weird pain-in-the-neck, multi-step operation (compared with, say, adding tags to your Flickr pics – how can it possibly be easier to manipulate meta-data in a web-based application than in a desktop app?) and you can’t tag iTunes tracks at all. Tagged tracks would really add a lot of value to the creation of Smart Playlists, for instance, especially if adding tags was really easy.