Has anyone ever written something with one or more people?

What are the pros and cons of doing that versus going solo?

My thought was that the pro would be that things would go faster and people could feed off each other for ideas. The con could be that they would get into arguments about story direction, etc.

Dawn

I've co-authored a couple articles, and one book.  I made sure we had similar writing styles and that I would be sort-of directing the whole thing.  I also had a very good legal collaborative agreement between us that we both signed before we got started.  In my case, it worked out fine. 

I have co-authored two business books with the same person and we divided the books into sections. Since we each brought different perspectives and skills to the table, we assigned ourselves the sections that we each felt the most comfortable with. Once we had completed the chapters, we traded them for editing and polishing so that the book would read as one voice. And that is the hard part when team writing: the book needs to have a consistent flow. The team also needs to have an agreed upon leader who will be the final authority in the decision making process. You are right about being able to feed off of each other when brainstorming. You are also right about things sometimes becoming argumentative and causing discord. But that's just part of the creative process :)