What is the True Covering Factor of Absorbing Matter in BALQSOs?
  Spectropolarimetry of Broad Absorption Line Quasars (BALQSO's) has demonstrated that the geometry of the absorbing material is far from spherically symmetric. Calculations of accretion disk spectra suggest that the intrinsic radiation pattern of quasars is also anisotropic. Because the quasar counts distribution is very steep, if the orientations of these two anisotropies are correlated, optical flux-limited samples would be very strongly biassed with respect to discovery of BALQSO's. In particular, currently favored models suggest that BALQSO's may be much more common than in the samples. If so, the intrinsic covering fraction of absorbing matter must be relatively large. Numerous consequences follow, including prediction of a new population of hard X-ray sources (as may have already been seen by ASCA), and a possible explanation of the anomalously strong NV~1240 lines seen in many high redshift quasars. 
J. H. Krolik & G. M. Voit