Microsoft’s No. 1 rival is a household name, Google. But a strong candidate for No. 2 is a company that is scarcely known outside the technology industry: VMware.”VMware is definitely a threat,” said Gary Chen, an analyst at IDC, a research firm. “After Google, it is the company Microsoft fears most.”Google and VMware pose a broadly similar challenge to Microsoft, by potentially undermining the dominance of its most lucrative products, desktop software and operating systems. While Google represents the attack from above, VMware is the assault from beneath.
http://www.nytimes.com/2009/08/31/technology/business-computing/31virtual.html