My sentiments mirror that of thefox.
Usually community collaboration projects/games, at least on classic consoles, tend to have 3 or 4 people at most. For example, Demiforce's Drymouth game involved only 3 people (coder/graphics, graphics, and musician).
The larger the number of people, the more likely there will be excessive amounts of pondering over minuscule things, or heated arguments over design choices (and never coming to full agreement). And if you have people who have large egos, eventually those can rear their heads and cause massive issues (i.e. someone leaves the project). Do not think even for a minute you can find a replacement by snapping your fingers -- it isn't that easy.
Back in the 90s I worked with Riff on our qNES emulator, which was just him and I. We never ran into any of those scenarios, but that's also because he knew a hell of a lot more than I did (esp. about things like cache lines and writing assembly code so that it fit within those cache limits -- something I still to this day haven't bothered to learn), and it made the most sense to accept his expertise, while I did other things (working on graphics code, trying to implement framework for mappers, etc.). But that's a different beast than, say, designing an actual video game -- a
**LOT** more is involved there.
To support all my claims, check out the following game called Cube World, which has been worked on by just *one guy* and he explains somewhere (FAQ, blog post, I forget) that he wanted it to be developed entirely by him (and the majority has been), but eventually branched out to get one more developer (not sure what their role is). And for efforts of basically 1 guy, it's pretty damn amazing:
http://wollay.blogspot.com/Now compare that to, say, large-scale Kickstarter indie game projects which consist of say 10-20 people, or commercial games which consist of probably 50 (not including any outsourcing, which is SUPER common; even Nintendo does this quite heavily!) people, and how awful those games turn out most of the time. No, not all the time, but most (IMO).