Thank you for the article and the debate; it's really interesting.
As you mention, gamification is getting into e-learning more and more, and I guess it's mainly due to the engaging aspects of game systems that it applies.
I think that a thorough analysis of what motivates people is key to better understand the importance of gamifying a course. Otherwise we end up with just 'PBLs': points, badges and leaderboards.
The interesting thing is to get someone doing something just for the sake of it, and this occurs more when what is done is intrinsic motivating. 'Players' or users, need to feel they're in control by having autonomy on the steps they take (as you mention) and also to feel that they're in relation to others whithin the gamified system.
A very interesting 6-weeks course is about to finish at Coursera:
https://www.coursera.org/course/gamification.