Besides domain age, what does this site have that makes it rank for every freaken term in the pet book: http://www.vetinfo.com
This might shed some light: http://www.seomoz.org/tools/page-strength.php?url=www.vetinfo.com%2F I think the biggest thing is the inbound links.
kinda frustrating as it goes against all that i've learned regarding on page seo. lol for example "dog health" they're number one, and their on page seo for that combo is horrible