On November 5th, the court sentences Saddam Hussein to death by hanging. I've already written earlier about Saddam's trial on GA. Therefore, most of the post today would deal with the idea of death penalty in general.
This is not an easy idea to live with, even with a mass murderer like Saddam (see Kriwrite's answer regarding Saddam's death toll, without counting post-1991 events!), and it is controversial in democracies, many of which have prohibited the practice.
In the United States, naturally and as well know, this is actually a well established practice. The oldest tree in New York, for example, is called The Hanging Elm, because it was used as gallows. It is currently legal in 37-39 states. However, only about 1.4% of all first degree murder cases in the US result in a death sentence; and only 10% of juries impose the death sentence when in comes to trial (see more death penality statistics gathered by Angy-ga).
There several social issues regarding this, like race (tutuzdad answered the question whether a white prisoner has ever been executed for killing a non-White person); the possibility of innocent persons being executed (sixteen such innocent persons have been executed in the United States since the 1970s). Naturally, there is also the question of coping and living with a death penality not to mention, again, the moral issue of taking another person's life. Here, it is interesting to note that 72.5% of the Americans who oppose abortions ("pro life") support the death penalty. The cost of prosecution, whether or not to ask for the death penalty or not, however, is not an issue.
It could be worse. As Keystroke notes regarding Singapore, some countries impose death penality also on crimes that are not murder.