Although I foresee a lot of those that register for the free online course dropping out. Most people won't put a high enough value on a free class, especially if they're not getting credit.
I also think that the instructors are going to be surprised when the 10,000 students come up with more than 25 interesting questions.
I wonder what happens for the students who need questions answered that aren't deemed sufficiently interesting or unique?
Both Sebastian Thrun and Peter Norvig are Very Important Persons in Google (Google Fellow / Google Director). This is basically a free diploma to be put in the CV for any Google wanna-be engineer, if they can make it. I doubt even credit would be more important than it.