@Martinghoul:
On the subject of assignment.
Let's say I established a Dec11 bull call spread (117/121) on SPY when SPY was at 116 (2 weeks ago or so). Let's say I hold it until expiration and SPY ends next Friday at 126. My spread is worth $4 at that point. However, I don't have enough funds on my account to either exercise the long option or get assigned on the short one and I did not sell the spread before close.
The margin requirement for the debit spread is the cost of the spread, so technically, I may not have any other equity in my account except for the spread value. What would a broker do? Will it exercise/assign automatically using their funds or something else?