Case in point:
This talks about both the Sony NEX and Micro Four Thirds. Should this have only the broader, generic tag, or should it have tags for both of the more specific systems in addition (or instead)?
If I'm using the exclusion feature of tags, and I hate Sony, I might miss out on a question actually interesting to me due to overly-specific tagging. Is that something we care about, or is it more overridingly useful to have more descriptive tags?