This happens, it happens behind your back, and it may *happen* to you. See County cuts off computer network
Now the background behind this is that the computer center people knew *nothing* about this, not having been consulted on how to set up a wireless lan. They got blind-sided by idiots who all along insisted they could maintain their own network thank-you-very-much.
One of the security people at another business I work at now periodically turns on the wireless station in his room just to see what might be broadcasting. I wouldn't be surprised to see him roaming the halls with a laptop open and running...