Using this simple setup: https://dl.dropboxusercontent.com/u/2068143/ShareX/2017/01/factorio_2017-01-08_15-11-48.jpg
There are certain times where unpowering the furnace, will cause the "unloading" loaders to keep unloading effectively infinite plates from the furnace. This seems to happen reliably when a power switch is used to turn off a furnace array as seen here: https://dl.dropboxusercontent.com/u/2068143/ShareX/2017/01/factorio_2017-01-08_15-12-53.jpg
Note that the chests weren't even close to full when the power was cut, but the loaders continued to unload plates from... somewhere...
Possibility that something related to productivity/speed and sudden power loss?
Using Arumbas Bobs+Angels (with UPS-up turned off)
Edit; it may actually be something else. It seems to pull way more items out of the entity than it actually had in it's inventory.