Both Coursera and Udacity are for-profit businesses, and both have yet to reveal (or decide) how they want to make that profit. Many current for-profit providers of education are not particularly well respected (University of Phoenix, Kaplan, etc). Some non-profit universities are understandable a little hesitant to work with Coursera and Udacity without a better understanding of how exactly they propose to make money (both have many suggestions, but nothing concrete as of yet).
This cynicism is one reason why some universities have decided to "go it alone" (MIT/Harvard/Berkeley being the most notable with edX).
To be clear, I'm not saying this is my viewpoint: I think very highly of both Coursera and Udacity. I just wanted to point out that some of the cynicism stems not from the idea of open access to teaching and knowledge, but from the worries over working with for-profit companies to achieve that aim.