Im in the middle of my own URL mess.

Lots of URLs..lots of sites...

From what I am gathering one should work with their main site dogfood.com and build. If there is a dogfood section and you are lucky enough to get such a specific product name as dogfood.com buy it ( why not) and have it point to your dogfood page or index page.

Use the extra URL's as pointers for now...down the road they can serve as their own site if you branch off.

Better to have the "I cant believe nobody owns that name" URL and use it rather than lose it to perhaps your competition. Heck, it don't cost much to own and you can always sell it too.

I wouldn't bother if it were not within a theme or as specific to the main site.