Tags Vs Free Text

What differences are associated with a MetaTag Tagsonomy compared to Free Text?

If you won't have a Shared Vocabulary (e.g. instead have Folksonomy), why not just use Free Text and a Search Engine?

Tim Bray on various Meta Data issues. He also asks the meta-question What am I doing categories for? What is anybody doing categories for? What is everybody doing categories for? see Social Network Context

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