Yeah, solid counterexample. Wikipedia and other Wikis have a clearly defined goal, i.e. collect factually correct information about a specific topic, which is also a goal shared by enough people to drive collaboration.

Another cool example is the Mutopia Project, which basically archives sheet music. Contributors can just pick a piece of music and transcribe that, and they kind of don't even have to talk to anyone for the project as a whole to benefit.

But then there is lots of examples, like writing a new song, writing a new novel etc., where the goal is not clearly defined, where it's difficult to collaborate, because what you contribute might not mesh well with what the others provide.