The best thing about open source is watching people from different backgrounds and skillsets work together to create something bigger than something they can could have done alone.
And, sometimes, the worst thing about open source is watching people from different backgrounds and skillsets work together to blow something up.
The Trail to You-Know-Where…
It is a common misconception that open source projects are magically self-organizing in a smooth and organic way. Everything comes together to software in the most efficient manner possible.
I'll wait while you stop laughing.
While it is true that collaboration in an open manner does typically lead to more productivity, the key thing to remember is that open does not mean "unmanaged." A big mistake that a lot of people do is throw out some code or documentation without clear guidance as to what needs to happen.
Managing goals is perhaps the most critical thing you can do when starting any collaborative project. Meetings, shared code, events… without a clear set of requirements for all participants to strive towards, a collaborative effort can often turn into a chaotic mess.
This does not mean, mind you, that those goals can never change. Sometimes people can have better ideas than what you had in mind, and you need to be ready to listen to new suggestions and be prepared to act on them should the need arise.
Having a plan does not mean being autocratic. It's like setting a trail in the woods: you can follow the trail and get things done along the way, but you are free to let folks wander off and try other things–as long as they know where the ultimate destination of the trail lies.