I have found on a fresh 1.1.2 install that the inventory does not reduced when an order is placed.
I have a configurable product called ‘tshirt’
Attached to ‘tshirt’ are two simple products - one for size small and one for size large.
Each simple product has 10 items in stock.
If a customer places an order for a tshirt in size small, there is no reduction in the inventory amount.
The 10 items remain.
It appears there is some disconnection between the order via a configurable product and the simple product that is attached to it.
Could someone please test to see if the same thing happens on their Magento version?