I personally think that while a dangrous development, a nuclear armed
Iran is not the nightmare scenario it is often claimed to be,and
rational analysis of the real dangers and likelihoods is needed, both in
public and political discourse. So agree to a large extent with this
article
http://www.guardian.co.uk/commentisfree/2012/feb/16/iran-false-nuclear-fears
After
all, the cold war subsided without armageddon, and that was a much
worse situation. One valid point however is that the mechanisms that
were developed between the US and USSR to prevent 'accidents'
(misunderstandings which could lead to reaction and counter-reaction)
aren't in place between places like Iran and Israel , and if Iran did
have nuclear weapons then the lack of such a diplomatic safety apparatus
would make it a very very dangerous situation. As the documentary 1983, Brink of Apocolypse
showed, even with these mechanisms, the world could and did come
frighteningly close to accidental annihilation during the cold war.
update : this following article also lists several reasons why a nuclear Iran might be containable :
http://www.guardian.co.uk/commentisfree/2012/feb/21/nuclear-alarmism-iran