It's said Xanax is the most addicting of benzos because it's extremely quick to take affect and also has the shortest half life of the other benzos. That being said, it was Klonopin, the slowest acting benzo with the second-longest half life (Valium has the longest) that brought me to my knees.
It amazes me that the literature manufacturers publish for their benzos states they should never be taken for longer than a few weeks, whereas most doctors write scripts for years.