That assumes that organized crime or organized terror are top-driven phenomena, so decapitation will kill the beast. But that is a rather simplistic view. Methinks, these are products of social relations, in which US foreign policy plays a relatively small role. These relations include the supply factor (the availability of people who for social, economic or personal reasons are willing to join terror/criminal organizations, and the availability of matewrial resources that enables those organizations to pursue their goals), the demand factor (the availability of people who are in the position to support and provide resources to these organizations), and the opportunity/transaction cost factor (circumstances that make certain courses of actions easier to implent than others).
Taking that into consideration, arresting leaders without destrying the social base for organized crime/terror will do little to root it out - as the prosecution of Mafia in Italy clearly illustrates. Of course, rooting out social causes does not necessarily involve a militray operation/occupation - but it usually requires it to carry out other measures.
As I see it, terrorism is product of three factors: overpopulation in central Asia and Middle east (i.e. the supply of large numbers of people who are economically marginalized), supply of material resources making terrorist actions possible (money, transportation, and efficient and cheap military technology), and the demand for terrorist organizations from the national political leaders at various point in time (e.g. Pakistan, US, Palestine, Iran, Saudi Arabia to name a few). Capturing the leaders of terrorist organizations without eliminating the root causes will at best make a dent in the tip of an iceberg.
Wojtek