We have an entire Citrix environment running at the company I work for. Anyways, when I was handling support desk, someone was having a printer issue. First thing I did was turn the printer off and turn it back on. Few minutes later...no one was able to log on to the Citrix environment, and all of the VMs were frozen. This meant that 90% of our users (smallish company) could not work. They could not connect to their XenApp or XenDesktop desktops. We had to force restart them. Whatever, coincidence.
Made a change to the printer server an hour later, restarted the printer...same thing happened. Took down the entire environment. Turns out the printer was not properly configured to the network (this was done way before I started working for the company).
But yes. I can say that I took down the entire production environment (CRM, Citrix, other important VMs) twice in the same day by turning a printer off and then back on.