On the empirical basis of six national studies (Mexico, Brazil, Peru, Denmark, Russia and South Africa), this paper examines the phenomenon of segmentation, defined as the solidification of deep hierarchies with little crossover between categories of institutions or individuals. The massification of higher education has brought about a great diversity of institutions and, concomitantly, stark differences among the professoriate. While the public sector has to some extent been able to protect its academic personnel, the for-profit sector is moving towards an unstable professorial, poorly paid, hired mostly on a per-hour basis, and for whom sharing in academic governance is a distant dream. Some of this differentiation is emerging also within institutions and a new kind of academic who could be termed "just-in-time knowledge worker" is on the rise.