I've had parts of an order cancelled, but only for 'sale' fabrics that were out of stock by the time they 'picked' my order. These were fabrics that they were not going to restock and they let me know via email that those items had been cancelled and why. They also email me if an item has gone on backorder and give an estimated date of arrival.
Backordered items from this particular supplier do not have to be reordered (I am given the option to cancel if I prefer however) and they will send them when they arrive. My CC is not charged until that time and I do not pay extra shipping. I'm very happy with the way they do business.