I was talking to my sister-in-law/editor, and she brought up some good questions about how a group might write collaboratively online in a wiki. It made me think more about how such a group might be organized.
In my mind, there would be several layers of participants. At the top, you would have one lead author. I've talked about this role before. One step 'below' the author you would have a group of folks whose input is trusted. They are either writers who can write close to the voice of the author, or editors who can clean up grammatical problems. I would think that there would be less than 10, probably more like 5-6 of these authors. Any more and it will be too hard to keep up with all of the changes. This group has full editing rights. They can go in and make changes to the text. Ultimately the author decides what stays and goes, but this group will be making contributions right within the text. Some of the writers may even take over a character, writing most of the 'voice' for that person.
Finally, below this group is a larger group of readers. These people would not have access to edit the text, rather they will spend their time reading sections and giving feedback. It wouldn't be the 'oh, that's a great chapter' kind of feedback. They would highlight sentences or paragraphs that were rough. Maybe they didn't understand this dialog, or they felt something was too obscure or obvious, or maybe they feel a particular character wouldn't have made that choice. The lead author and the secondary authors would decide if they needed to alter the text based on the feedback. It may be that the readers, and even the secondary authors feel something is amiss, but ultimately the lead author must make the decision about where and how the story unfolds.