In this work, we have constrained the Compton cloud model for the broad iron line in both MCG-6-30-15 and NGC 3516 by considering two observational constraints which are independent of the detection of a spectral break in the continuum spectrum: the continuum variability timescale and the absence of an observed soft excess. We have then demonstrated that the constrained model requires a continuum source which violates the black body limit. We also point out that the difficulty of photoionizing the Compton cloud to the required levels. Thus, we rule out the Comptonization model for the broad iron line in MCG-6-30-15, and show that fine tuning is required in order for the model to explain the line in NGC 3516. We conclude that the combination of relativistic Doppler shifts and gravitational redshifts still provides the best explanation for the broad iron lines seen in AGN.