It would be interesting to know how many applicants got interested in Computer Science from watching Stanford's excellent iOS courses on iTunesU. Additionally, it would be interesting to learn how many students declare Computer Science before they enroll and how many students switch into Computer Science because "all their friends are doing it" now that it's the most popular major.
I don't know how many people were inspired by the iOS class, but it doesn't seem to be super popular on campus. I do know a fair amount of people (myself included) who had never programmed before Stanford and were simply motivated to keep going after the introductory sequence. There's definitely a snowball effect, but it wouldn't happen without a great curriculum.