It is no secret that faculty evaluations at top universities weigh research much more than teaching. This is not surprising given that, among other reasons, global visibility comes from academic innovation (think Nobel Prizes) not classroom instruction. Come promotion time the peer review system carefully examines your publication record and ability to raise research funds. External experts within your research area are asked if you are a leader in the field. Top universities maintain their status by imposing standards that lead to a highly competitive environment in which only the most talented researchers survive.
However, the assessment of teaching excellence is much less stringent. Unless they reveal utter incompetence, teaching evaluations are practically ignored; especially if you have graduated numerous PhD students. Certainly, outside experts are not asked about your teaching. This imbalance in incentives explains why faculty use research funding to buy-out of teaching and why highly recruited candidates negotiate low teaching loads.
Top researchers end up at top universities but being good at research does not necessarily mean you are a good teacher. Furthermore, the effort required to be a competitive researcher leaves limited time for class preparation. To make matters worse, within a university, faculty have a monopoly on the classes they teach. With few incentives and practically no competition it is hard to believe that top universities are doing the best they can when it comes to classroom instruction. By introducing competition, MOOCs might change this.
To illustrate, say you are a chair of a soft money department in 2015. Four of your faculty receive 25% funding to teach the big Stat 101 class and your graduate program's three main classes. But despite being great researchers these four are mediocre teachers. So why are they teaching if 1) a MOOC exists for each of these classes and 2) these professors can easily cover 100% of their salary with research funds. As chair, not only do you wonder why not let these four profs focus on what they do best, but also why your department is not creating MOOCs and getting global recognition for it. So instead of hiring 4 great researchers that are mediocre teachers why not hire (for the same cost) 4 great researchers (fully funded by grants) and 1 great teacher (funded with tuition $)? I think in the future tenure track positions will be divided into top researchers doing mostly research and top teachers doing mostly classroom teaching and MOOC development. Because top universities will feel the pressure to compete and develop the courses that educate the world, there will be no room for mediocre teaching.