The IRS is not paying $11M for the development know-how to maintain security; it's true that they could probably shop around and find the services they need for much less.
No, they're paying $11M so they can say "We paid Microsoft $11M! What else could we possibly do?" when something goes wrong.
Something tells me you did not understand the above comment... He's saying the IRS could shift responsibility based on the fact they paid the worlds biggest software vendor 11mil... Switching to Linux puts the responsibility back in the IRS's court...
No, they're paying $11M so they can say "We paid Microsoft $11M! What else could we possibly do?" when something goes wrong.