Here is a somewhat interesting article on the small trend of authors opening up their manuscripts to collective writing and editing.
Having just worked collaboratively with my colleague for the past three weeks using the great product called SubEthaEdit, I can say that this model REALLY needs to develop. I mean that in two ways: the tools need to get better, and it is a fantastic way to work and we really need to see it happen for that reason.
I asked one of the creators of SubEthaEdit if they were going to develop a rich-text version. He said that IF they ever did, that they would use the now-in-place networking code but build a rich-text editor on top and put it in a completely different product. He of course finished by saying “we can not comment on future product.” I couldn’t tell if that meant they were doing it or were not even considering it. I would highly recommend that you email them if you would like to see a rich-text collaborative text editor (that can read/write Word docs including tables and headers/footers.)