I have always considered it finite. As you can see from our Manifesto (written almost a year ago now):
"Attention is what you care about. It is a resource that is quickly evaporating as an avalanche of information sources clamor for your time."
David also quotes John Hagel's post "the economics of attention" which is Amazing.
I dare not quote any one part of it here because it is, in its entirety, a wonderful summary of the relationship between Attention and Economics and future Markets which itself pulls from quotes and summaries from other definitive sources.
Our Manifesto, by comparison, looks simplistic at best. The key for us, however, is not how Attention may affect markets on a macro scale. Nor is it about how companies can get, keep and leverage your attention. Our/my interest is in the individual. Me.
How can I, during my ordinary, everyday life, maximize my time by filtering out the noise and receiving information, products and services that meet my needs and expectations at any given time.
How can I, in an increasingly Attention Savvy marketplace (where companies are mining and using my Attention Data), take control of my Attention rather than ceding control to others.
From this perspective, I think the issue becomes far more manageable. And the value to the user becomes far more practical.
This is not a fight the system proposition however. On the contrary. It is a commercial exercise. The user has an urgent and growing need to take back control in order to bring balance to the system. And when there is a need, there is demand; and where there is demand there must be a supply.