Statistical analysis of terrorist groups' longevity, aims, methods and successes reveal that groups are self-contradictory and self-sabotaging, generally ineffective; common stereotypes like terrorists being poor or ultra-skilled are false. Superficially appealing counter-examples are discussed and rejected. Data on motivations and the dissolution of terrorist groups are brought into play and the surprising conclusion reached: terrorism is a form of socialization or status-seeking.
http://www.gwern.net/Terrorism%20is%20not%20about%20Terror
Modeling terrorists as trying to kill as many people as possible strikes me as insufficient. In Terror and Consent, Philip Bobbitt models their aims as propagandistic, which feels more like the right angle---hence the focus on inefficient but spectacular killing.
Incidentally, I've expanded my above comment into an essay called 'Terrorism is not Effective' (http://www.gwern.net/Terrorism%20is%20not%20Effective).