The "what is and isn't SaaS" debate comes up again

This question seems to pop back up every couple of months:

Does a SaaS relationship have to be between two different companies or can it be between internal IT and business users within the same company?

Now it's Todd Biske and Joe McKendirck re-igniting the debate.

My view hasn't changed much since the last time this went around. Saas formalizes and standardizes what business and IT leaders have been discussing for years. The business agrees to specific business requirements and to a minimum platform (in most cases, a standard browser). IT (or external provider) agrees to meet those requirements with a minimum SLA. How the bill is paid or what corporate entity owns the datacenter are secondary logistical concerns and not central to grasping the importance of what the SaaS model brings to the enterprise.