Green IT?
One of the main advantages of going to virtual servers is reducing your power and cooling needs.  Reducing servers also has the added advantage of reducing the amount of power needed to run the environment.  This can have significant environmental advantages as you can reduce your carbon footprint significantly.  A tree will remove approximately 2.52 pounds of CO2 in day.  By reducing power consumption you can reduce emissions which frees up trees to filter additional CO2.