Today's New York Times report (4/25/11) on the WikiLeaks Guantanamo files provides an answer:
The documents show that a major reason a Sudanese cameraman for Al Jazeera, Sami al-Hajj, was held at Guantanamo for six years was for questioning about the television network's "training program, telecommunications equipment and newsgathering operations in Chechnya, Kosovo and Afghanistan," including contacts with terrorist groups.
The Times' piece is definitely worth reading, though I wish they didn't feel the need to add this type of equivocation:
The Guantanamo assessments seem unlikely to end the long-running debate about America's most controversial prison. The documents can be mined for evidence supporting beliefs across the political spectrum about the relative perils posed by the detainees and whether the government's system of holding most without trials is justified.
This would seem to be true of most policy debates about controversial subjects, so it doesn't seem worth noting.