Cloud computing platforms like Amazon.com’s EC2, Google’s App Engine, and the Sun Grid all act like huge collections of powerful virtual machines. Developers can set up their applications on their own virtual platforms, then migrate those applications to EC2 or the Grid with readily available tools. Presto! The new software becomes available for the world to see. Production servers are moving onto these clouds and out of smaller corporate datacenters, which some observers think will reduce the addressable market for virtual server software from VMware, Citrix Systems, and Microsoft. Cloud operators like Amazon win in that scenario, as do regular old IT managers. The losers? Virtualization experts.