The problem is that most of these forms of learning are one-size-fits-all. Each of us has different learning preferences, speeds, and focuses. You may be interested in Java, I may be interested in C#. Should the learning provider create versions of classes in both languages, and invite people to one or the other, or should they create one class that teaches concepts and techniques, and assume that the language doesn't matter?
When you are the provider, you are forced to make specific decisions about investment and potential return on investment each time you consider these options.
Community ownership will offer a very different set of options. There is no cost (at least, beyond that of some individuals or groups who donate their time). There is, therefore, no consideration of return on investment.
Let's say that I see a challenge that addresses a particular technique in Java. "Oh, that's cool! But most of my friends don't speak Java - they speak C#. Hmm." At that point, if the challenge moves you to take action, you can create an alternate version of the challenge (the "quest") in C#, share it with some other C# folks in the community to get their agreement, and make it available to the general Mastery Quest community.
Of course, key to this is my idea that all quests serve three purposes:
- Gaining real, useful experience