There should be frequent reorgs, and not all of them should be communicated to everybody. This actually happened to me at Netscape: my group got moved to a different department, and nobody told me until the admin of my old department came by with my mail and told me I should be using the mailstop for my new department. (In 2.5 years at Netscape, I went through 10 reorgs.)

To crank it up a notch, you could have people getting silently reorged into new responsibilities, and then they get in trouble for still doing their old jobs.