Anything which encourages the use or development of proprietary systems that are difficult to certify for even the most basic levels of security creates additional risk to computer systems; reducing government support for security development for any widely- available and widely-used operating system creates additional risk; and suppressing the development of a competitor's secure software on the basis of market concerns creates a security risk for your customers as well as your competitor's customers.
http://www.theregister.co.uk/content/55/26866.html

! this is a realy good read !