In regard to the schema.org Organization markup... is this only to be marked up on the homepage or should it be on all pages?
This is from the Google Webmaster Central Blog :
"For example, a business whose homepage is www.example.com can add the following markup using visible on-page elements on their homepage"
It is this comment that leads me to believe it is only to be marked on the homepage, similar to how rel=publisher is only required on the homepage (yes, I know that is not schema related really).
What is the verdict? It probably won't do anything, but might as well mark it up - it can't hurt is how I see it.