Better Tagging: Wikidata as a Controlled Vocabulary
Wikidata provides a very large set of structured, multilingual concepts. It's essentially a community controlled vocabulary, complete with stable identifiers and rules about scope and granularity. It has more than 10 million entries, is freely usable, and reacts a lot faster to real world changes than most other such vocabularies. This makes it an excellent tool for tagging content in a way that directly ties it into the linked data web.