How about SAP, Oracle Databases and other complex architectures in the Cloud Space ?
SAP comes in two flavors in the Cloud Computing space. One is pretty simple to define and describe:
It is the typical SaaS Solution:
SAP Business ByDesign. Simple pricing model, but there is not too much of long year experience in the market, as this Software solution is pretty new....
We will here focus on the Standard SAP Business suite. These SAP Applications are a central part in larger companies. They build a design backbone for the infrastructure.
At this point, standardization is key to your envoronment. Use simple, but effective Operating Concepts. Use Solaris and/or Solaris x86.
You may find excellent information about SAP Infrastructure Solutions including detailed recommendations for setup of more complex environments like Oracle RAC at The SAP on Sun Wiki