The CIA is blocking the release of information because the subject remains sensitive—both for the West and the Muslim world. In Washington, the CIA could come under fire if its own archives would confirm and fill out the current sketch view of history. For the Brotherhood, amid its current re-emergence as a major political force in Egypt and other countries, it would be extremely damaging to know that illustrious figures in its history were working for the country that most exemplifies the decadent, imperialist forces it has struggled against for decades.
Remember that the English agent John Philby was the chief counsellor of King Ibn Saud, the usurper of the custody of the Holy Places, who made of the Wahhabist heresy the official ideology of Saudi Arabia. The Wahhabist kingdom, historical ally of Anglo-American imperialists, has generously financed and supported the Islamist groups. Now these groups have found another Wahhabist cashier, the Qatari Emir; housing Aljazeera and the regional seat of US Central Headquarters, Al-Thani is trying to adopt a role of leader in the Arab world and has become the main competitor of Saudi Arabia in the pro-American coalition. This way, who pays for the musicians, decides the music, which is after all an American music.