Kidnapping has long been a favorite weapon of terrorists. Killing people is one thing, but when you kidnap them, the terrorizing effect lasts much longer. In Iraq, over 200 foreigners have been kidnapped so far (as of the first week of June). Of those, 17 percent were killed, 47 percent released (with, or without, ransom), three percent escaped or were rescued, a quarter are still held, while the fate of the rest is unknown.
Most of the Iraq kidnappings were by Iraqi gangs of Sunni Arabs. These guys eventually lost interest in nabbing foreigners, mainly because it was easier, and safer, to go after Iraqis. Over 90 percent of total kidnap victims in Iraq were Iraqis. Grabbing Iraqis was not risk free either. Most Iraqis belong one of the hundred or so tribes that define Iraqi society. If you kidnap someone who is particularly well connected in tribal circles, you are in big trouble. Al Qaeda learned this the hard way when, in late 2004, they began kidnapping tribal leaders as a way to maintain tribal support for terror operations. This tactic backfired, as the tribes saw red and came after al Qaeda. Caught between deadly American troops and angry Iraqi tribesmen, grabbing foreigners suddenly seemed less important. Aside from the long shot chance that taking a foreigner might get some foreign troops removed, its just too much trouble and too risky. This is especially true as there are more Iraqi police out there. Take a foreigner, and word tends to get out on the street. If the Americans pick up your scent, it can get real ugly, real fast. Thus the vast majority of kidnap victims are Iraqis.
The kidnappers have a new problem; Iraqi police. The kidnapping is, like suicide bombers, very unpopular among Iraqis. With more police in service, there is more opportunity for Iraqis to tip off the cops about where kidnap victims might be held. Increasingly, police raids are finding and rescuing kidnapped Iraqis, and, recently, a kidnapped Australian as well.