I would agree that turning data centers green is a shares responsibility. In the data center space, we strive for more energy efficient design and have done things like upgrade the efficiency of our power supplies. Our new Cisco Nexus 7000 supports front-to-back airflow for better cooling efficiency and we just released a version of the Catalyst 6500 that does the same.

However, the network is usually responsible for only 5-15% of the power/cooling load in the data center. Our belief that real progress can be made by helping customers extract more value out of the power they do consume, hence the emphasis on virtualization as a mechanism to accomplish that. Here is a good blog posting on the potential and what it will take to get there: http://communities.intel.com/openport/blogs/server/2008/01/29/almost-free-data-center-capacity

On a related note, we also expect to see a unified fabric as a way to also increase DC energy efficiency. Some initial numbers we have gotten from analysts indicate the initial costs savings wold be ~8% of your DC energy bill.