ISIS and other Middle Eastern groups are notorious for kidnapping. However, for radical Islamist groups in the Sahel and northern Nigeria, ransom is also an important source of funding. In Nigeria, and probably elsewhere, most of the victims are indigenous. Families of kidnapping victims routinely pay to secure the release of loved ones.
Kidnappers may widely publicize foreign victims, generating considerable pressure, especially on European governments, to pay ransom. Though they all deny it, there is plenty of evidence that they cave to popular pressure and pay, in some cases many millions of dollars. That, of course, merely leads to additional kidnappings.
The United States is an honorable exception to this pattern. The policy of successive administrations has been never to pay ransom. A consequence is that there is evidence (again, largely anecdotal) that kidnappers are less interested in American citizens than in European nationals. The tragedy, of course, is that if Americans are part of a kidnapped group of other nationals, their likelihood of surviving is low; there is no incentive for the kidnappers to keep them alive, unlike other nationalities who are a valuable commodity.
The New York Times reported on November 19 that the Obama administration is reviewing its policy on American hostages, but it has reaffirmed that the ban on ransom will not change. This is wise.