Hi, there is a book on this topic:
"Gamification by Design: Implementing Game Mechanics in Web and Mobile Apps", written by Zichermann and Cunnigham, from O'Reilly, August 2011.
The description on amazon mentiones case studies. I haven't read this book, I have just seen it in the book store, so I can't tell you if it is good or if it is what you are looking for. There are no customer reviews yet, but I hope that this information helps.
