If you have a look at the edit history of this question, you'll see there's been a minor tag edit-war (not really - all genial, see the comments on the question itself :) ).
I originally put quite specific tags on, but tags that I think (and hope) are likely to be more used in the future. Most of the tags were non-existant, or only had one or two other questions. IRO-bot replaced these with more popular tags. I would totally agree with this if I thought the original tags were unlikely to be used much in the future (or were likely to turn into a useless mess). But I think these are potentially useful. They would be even more useful if there was a hierarchical tag system on SE, but I don't think there is (although sub tags, like ocean-models, can be mentioned on the oceans tag wiki).
So, the question is, how specific can tags be? Should we already be expecting questions to mostly stick to using existing tags? (I'm worried if we do that, that we'll later have to spend a lot of time re-categorising questions into more granular tags).