Paolo Valdemarin, who has been thinking about tagging as long as anyone, is still not a "believer." Upon Technorati's 1 millionth tag, he points to the need for more sharing and gardening tools, but also practices:
But look at Wikipedia: it's a totally bottom-up project which has some very simple but strict policies and guidelines about how it should be developing. Writers are respecting these rules, finding new ways to enforce them and the whole system is blooming beautifully.
Tagging has already grown into a rich and barely comprehensible ecology. There is a role for rules where groups want to coordinate. But these can be implemented through either tools or practices, and tools tend to hard code against emergence.