According to http://docs.scala-lang.org/news/functional-programming-princ..., 50 thousand people signed up for scala class, and about 9.5k people finished it successfully.

I've been signing up to some courses in coursera.org, and some classes at the end send out statistics. Another class "Programming Mobile Applications for Android Handheld Systems" recently sent me email that 220k students signed up, and about 7k students will pass it.

So percentage of signups to successes is small compared to college classes, but if you look at '7k' or '9.5k' completions, it's rather impressive.