K P wrote:
If you break down a family into genera, then you can wind up with something from one of the big families, where you have 5 genera with 100 members each and a couple of thousand genera or categories with only one member each, again, you haven't done anything useful.
I expect the way this would be done according to existing common practice on Wikipedia would be to create subcategories for those five genera with lots of members, and then the remaining thousand species that each belong to their own genera would remain under the root family category. People don't generally create categories that will only ever hold one or two articles, there's no point.
That's assuming all of those species even get articles, of course.