A growing concern is the growth of the "Islamic gangster" element in the criminal underground. With the disappearance of nations where terrorist training facilities can be maintained, there is no way to prepare, and evaluate, candidates to be really effective terrorists. Even all the violence in Iraq has not been much help, as the average newbie terrorist there gets, at most, a week of training before going into action (and usually getting killed or captured during the first few missions.) To compensate, the terrorist groups have been relying more on, well, mercenaries. That means you hire whoever you can to provide technical, or specialist, services. This has become big business in Iraq, where criminal gangs, or pros formerly on Saddam's payroll, have been doing their thing (making bombs, scouting, forging documents, spying), for a price, for whichever group is offering the best deal.
In many parts of the world, the professional criminals want nothing to do with terrorists. That's because of the additional police attention given to terrorist activities. A successful criminal wants to stay out of jail, and alive. Working with terrorists makes it more difficult to do either. But in some parts of the world, where most of the crooks are Moslem, it's not so hard to find professional criminals who can be convinced to help the cause of Islamic terrorism. What's more worrisome, both to police and terrorist leaders, is the increasing number of criminals, and terrorists, who move back and forth between both worlds. This is not good. Technically, the criminals are sinners that the, more religiously pure Islamic terrorists, don't want to become contaminated with. But many of the lost souls who wander into terrorism, find the criminal life lucrative, and appealing. However, gang bosses don't like guys who might go back to being an Islamic terrorist. But what are you gonna do? If a guy is good at what he does, you have to indulge his weaknesses. Even terrorist leaders are inclined to cut their followers some slack. For the police, it's a nightmare, as there are far more gangsters than terrorists out there. The terrorists are a more fragile bunch, and more prone to just dying out. But the crooks will always be there, and if a lot of them get cozy with Islamic terrorism, so will the terrorist activities.
Historically, terrorist organizations tend to mutate into criminal gangs. That's how Italian, Corsican, Colombian, Irish, and other, terrorist organizations became organized crime groups in the last century. The Islamic radicals are following the same path.