Tim talks about the importance of having separation and visibility between front-end and back-end service traffic. We are seeing this use case more often as more web products are being built off the same API that is opened to customers and partners. Because your web app is the biggest customer of the API, it's critical to be able to understand and throttle traffic into the back-end to make sure your web app performance isn't compromised by API usage by other clients.
From a competitive standpoint, Tim makes a great point that it's critical to be able to assure enterprise customers that a SaaS API is as robust as anything their customer could build or buy on-premise - not only from a functional standpoint, but operationally in terms of security, compliance, control and scale.
For more on this, Dana Gardner did a great podcast on Innotas API management at briefingsdirect.com