Attacking an Embassy is considered an act of war, because the ground the building stands on is agreed to belong to the hosted country. Considering the US/UK presence in Afghanistan and Iraq, it would be really easy to attack Tehran.
I just hope they consider that.. The initial reports in Iran, of hostages, was quickly buried.
I don't know who stoked these "students" into attacking the embassy, but they did a good job of it. Every Iranian I talk to outside the country, calls the "government" (dictator) there "crazy".