The nature of the dominant power source in ultraluminous infrared galaxies (hereafter ULIGs) has been the subject of intense debate, ever since their discovery in significant numbers by the all-sky survey carried out by the Infrared Astronomical Satellite (IRAS). The debate has intensified once again following recent mid- and far-infrared spectroscopic observations of ULIGs by the Infrared Space Observatory (ISO), and is the main theme of this workshop. The scientific organizing committee (SOC) asked the conference participants to form two teams (with meeting rooms in the ``blue tower'' and the ``green tower'') charged with marshaling the evidence in favor of starbursts and AGNs respectively, in preparation for ending the conference with a ``Great Debate''. This article presents the evidence assembled by the ``green team'' as to the fraction of the total bolometric luminosity of ULIGs that can reasonably be attributed to dust-enshrouded AGNs, and answers additional questions posed by the SOC on the relevance of ULIGs to galaxy transformations.