Where do you see the difference between Application Service Providing and SaaS?

When I posted the article "What does SaaS mean to you?", Dan D. Gutierrez made the comment:

My firm launched the web's first web-hosted database service in 1999 when the SaaS industry was called Application Service Providers (ASP)...

IMHO the distinction between SaaS and ASP is very subtle. Andreas Müller of WIN-Verlag GmbH & Co.KG recently asked me:

Where do you see the difference between Application Service Providing and SaaS? Why do we need this new acronym?

SaaS is typically delivered through an Application Service Provider (ASP). So SaaS relates more to how a product is sold – how you as a customer have chosen to purchase. ASP is the delivery mechanism that enables us to get it to you. If you buy a book online, it’s currently delivered to you by mail; however, there are companies that are experimenting with delivering chapters online through a subscription model. It’s the same with software. Autodesk customers purchase Collaborative Project Management solutions like Buzzsaw, Constructware, and Streamline, and energy analysis tools like Green Building Studio with subscriptions. We deliver it to them via the Web.

Do you agree with my assessment? Are am I splitting hairs? Let me know what you think at TheLabs@autodesk.com.

Pondering the meaning of four one-thousandths of a picture is alive in the lab.