(What template exactly are we talking about here? I noticed that I might be talking about something different after I was done typing already.)
That's kind of what I was originally going for with the whole modular/extensible infobox approach, but then I became lazy, took way too long to finish the base InvItem template, then I realized that my initial implementation was less than ideal in certain regards, then odd bugs started appearing, and then the code editor disappeared. *looks over to RZR0*
Anyway, I'd say infoboxes shouldn't do too much automatic categorization. I'm fine with categories like Blocks, Tools, Enchantments, but specific stuff like "Wands (Thaumcraft 4)", "Computer Peripherals", "Spell Components" shouldn't be done by the infobox. Those would require too much specific code in the infobox template that does nothing but add a category.