Rather than a physical location, the enterprise now seems to be more nebulous and "logical" or "conceptual". It now can be seen to expand possibly, with the cloud, as the amorphous mass expands so does the virtual enterprise. This is where the enterprise merges with the eco-system and you see the emergence and need for addressing aspects of the eco-system that span physical and logical enterprises. As we needed enterprise architecture, for the cloud we need an eco-system architecture.
Eco-systems are more dynamic, opportunistic in some instances; some shorter and some longer enduring alliances between interested business parties. This not only affects the IT side, as it were, in a "bottom up" fashion, but also the business architecture; in a more "top down" manner.
The structure and function of a business is defined by its model of what goods and services it provides and consumes; who it needs to partner with at what point in its dynamic existence. This relates to policies that cut across and senses the eco-system for more appropriate alliances and takes competitive advantage of this new configuration. A business architecture in an eco-system architecture is then configured by rules and policies driven by competitive business goals, not statically defined.
The cloud provides a virtual rockbed for the reconfigurable enterprise that supports its dynamic business architecture to sense and respond, anticipate and adapt to the ebb and flow of trends in the eco-system. The eco-system architecture defines and configures these elements that include the traditional business architecture, multiple enterprise architecture plus a set of rules, policies, that define desirable (to be sought) and undesirable (to be avoided) configurations of the business and IT as they ride on top of the virtual infrastructure provided by the cloud.
This constitutes the eco-system architecture of the future.