There is a warning against such things in the user's guide:
If you create a new page or edit an old one please add it to one or more matching categories to facilitate navigation. Please do not create new categories (especially not ones with only one entry) unless you are sure they really will be used. A good criterium may be if it fits well in the hierarchy below. Try to keep the number of categories on Meta-Wiki as low as possible - categories are useful only if people can remember which categories exist and what their purposes are. If you have to look into three almost equal categories to find the page you are looking for, something is wrong with the system. Categories without a description, with too few member pages or which are not listed here may be removed.