What to do with subcategory domain names?

In relation to the category domain name?

[HughMungus]

I saw Webwork say that some domain name questions are really SEO questions and since I didn't get many replies about this situation over there I thought I would post it here where it supposedly belongs.

If I have the domain name example.com where "example" is a big category of products with lots of subcategories, should I register the subcategory domain names, also (e.g., green-examples.com, red-examples.com)? I'm thinking that it would be good to have websites that are more specific to the subcategories since people might search for the subcategory of product but not necessarily the main category of product.

Exemplified: math is a big category but people might be searching for information on algebra, geometry, etc. without ever using the word "math" in a search. So should I get algebra dot com and setup a mini site using the same DB but with ONLY algebra product listings? Or should I have a bunch of text with all details being on math dot com?

On a related note, how do the search engines view this?

[caveman]

Personally if they're thay closely related I keep it all on one site. Reasons:

- larger, richer site
- lots of context and easy for users to find related items
- more opportunities for deep links
- easier to manage
- less spammy appearance.