Quoting from the XenSource official announcement:
XenSource, Inc., the leading provider of enterprise-class virtualization solutions based on the open source Xen hypervisor, today announced that it signed its 1000th customer in Q3. The introduction of the feature-rich, high-performance XenEnterprise v4 in August accelerated this growth, helping the company nearly double its customer base. New XenSource customers include ASIERUS, Carsdirect.com, Cornell University, McKesson, Miami Herald, Microsoft, Polycom, Postini, Raytheon and Sleek Networks. Additionally, XenServer and the freely available XenExpress also experienced record customer traction, with more than 25,000 downloads of XenExpress occurring in Q3…
XenSource announced the 500 customers goal in July 2007, so it only took 4 months to double the customers base.
It’s worth to note that among its customers XenSource has Postini, which has been acquired by Google. So in some ways Google is now using virtualization technologies. A strange thing since the search engine stated