Anyone who has ever seen a TV show or movie centering around extortion knows that giving in to the demands of the extortionist only makes him want more. Somehow, Spain failed to learn that lesson as evidenced by the Spanish al-Qaeda aligned group's demand that Spain leave Afghanistan, Iraq and stop supporting the US, as this article shows.
Jonah Goldberg has the right take:
If [the above story is] true, the conventional wisdom about al Qaeda winning a victory by knocking Spain out of the coalition shouldn't be overturned so much as revised. If that had truly been al Qaeda's goal they would have been very, very smart to pocket the victory and attack Britain or Poland. Instead, by increasing the attacks on Spain they underscore the stupidity of Spain's appeasement since that appeasement bought Spain nothing.