"Sales Ready Leads": Where does this definition live?

I was watching Brian Carroll's webinar, "A Multimodal Approach to Lead Nurturing for Comples Sales". One of the key points that Brian made on the webinar is the need for Sales and Marketing to agree on the definition of a "Sales ready lead". This got me thinking, "Where does this definition live? Most Marketing organizations I have worked with use a mix of technologies to manage their Marketing campaigns and end up bringing Leads from these different systems directly into their SFA system. For example, web inquiries, attendees from online and offline events are directly brought into SFA systems like salesforce.com.

The key is to have a Lead Management solution that sits between Marketing and Sales systems and holds the definition of the "Sales ready leads".