Wow! Now I want to write apps. Other platforms like PubSub should follow Flickr's lead: clearly document the APIs and be API religion agnostic by offering APIs for the 3 major cross platform religions: REST, XML-RPC, and SOAP.
From Flickr Services:
The Flickr API is now available for non-commercial use by outside developers.
For an example of an application built with this API, see Organizr (or here if you are already a Flickr member).