Tags are needed similar to SE. For example board game category might want tags to differentiate between miniatures, card games etc…
Is there any work being done towards supporting tags on posts? There are valid usecases, for example a company using a similar category distribution as here in meta might want to tag posts by product (eg a product does not justify a category but someone interested in everything related to a specific product can just search by tag).
There are 2 better tags feature reqs out there