Gamification: The Art of Attracting and Keeping Users
drdobbs.com
drdobbs.com
That said in the way it's outlined it is maybe better than the old "carrot and stick" approach, which is in effect what it is. Suppose in many ways it is getting word of mouth and making it marketable. If you have a good product then the customers will come and stay, though if you make drastic changes to gain new clients/customers you may alienate your existing clients/customer base. No golden solution to be found here.
Saw a presentation a while ago that hooked me, can't watch it now, but think it was this one:
http://www.youtube.com/watch?v=7ZGCPap7GkY http://www.slideshare.net/dings/meaningful-play-getting-gami...