Why doesn't MS just pack up and move somewhere else?

Microsoft currently enjoys an arguable monopoly on a global scale, but proponents of this argument advise risking the loss of the richest market in the world, the United States, in order to "make a point". In order to conduct business in the U.S., Microsoft would still have to abide by commerce laws. Failure to do so would simply open the door wider for alternatives to emerge here in the U.S., a risk of losing the U.S. market altogether. As for the economy, yes, Microsoft is indeed influential, but they are not a breaking point. If MS were to leave, the U.S. economy would still carry on.

Also, all of the above does not take into account that Microsoft is a publicly owned company, and a decision to move the company out of the United States would be up to the stockholders and not Bill Gates and Steve Ballmer. And it is highly unlikely that the stockholders would support such a proposed solution to government intervention.