Well let me tell you that using ICBMs is not a valid way of "encouraging" a Civ to come to the table with a lot of goodies to exchange for peace. I nuked the Americans (sorry

) a few times with ICBMs, targetting their capital and two other largest cities. Not only did they refuse to make peace, they got the rest of the world on my case. Let me tell you that being very technologically advanced doesn't always bring about much benefit, especially if they have bombers. The malfunctioning of the Air Superioriy option for interceptors really makes it a pain in the buttwhen they send wave after wave of bombers to destroy you terrain improvements.
The only nukes I choose to launch are the tactical ones, and only at ships. They're great at taking out naval task forces, without the pollution (so I believe) and global reprisal. But it's a two way street; if opponent civs have them they'll probably end up using them on you and your cities as well.
ICBMs, as far as they fit into my strategy, are useless and can end up being more dangerous to yourself than the intended target. They're expensive, not very damaging (only half pop and half chance of killing military units) except when dealing with your reputation, plus they render the city you nuked pretty weak as the intense heat produces global warming effects in the immediate tiles (9).
I only build ICMBs for one ofthe same reasons the Cold War started; to make sure I can retaliate if the other guy chooses to use his. From my experience, you probably need to really infuriate your opponent before he uses one or more.