And why should they release their headcount unless other companies do the same? All releasing that info does is make them a lightning rod for criticism by politicians who need someone to bash, especially while the anti-business party is in power.
IBM needs to do whatever they have to to survive and compete. If the US has made it difficult, the natural response is to shift resources elsewhere. If the govt. seriously wanted to get businesses to come back here instead of fleeing, they'd get rid of corporate taxes. All of a sudden the US would be a tax haven for business, jobs would come here as businesses relocated to the US, and we the consumers would not get stuck subsidizing corporate taxes. After all, if the govt makes it more expensive to do business here, a corporation must either 1) move to a better tax climate, or 2) pass along the costs in their pricing. All the additional jobs would raise lots of money in payroll taxes, social security and medicare would be better funded due to the increase in jobs, and the US would be much more competitive in the world.