ACTION-278: CSRF defense use case?

Tyler,

I think it would be useful in this discussion to have a CSRF defense
use case on hand, since that's where this discussion started [1]. Can
you provide a simple but somewhat realistic scenario where unguessable
URIs might be helpful in CSRF defense?

Thanks
Jonathan

[1] http://www.w3.org/2001/tag/2009/06/23-minutes.html#item05

Tracker, this is ACTION-278