i agree with you, and i think it's a good candidate for throwing spaghetti at the wall. pick some managed tags that represent the personality of the site as you envision it, and sub them in/out as your vision is refined, like a benevolent dictator guiding an empire. managed tags + suggested recent popular user tags would be a fun way to keep things taxonomically viable but also add some chaotic stress/pseudorandomness to invite opportunity for change/evolution/whatever.