Yes, people need to bring - or to make - their own content. As you explain, the main challenge in such designs is to integrate everybody's experiences into a coherent whole. We want to avoid the feeling of Babel - everybody speaking a different language!
How can some common analysis of big WHYs happen? How can I look at your footprint and you look at mine in ways that we can see similar big SO WHATs? Your footprint looks like a butterfly and mine has a big protuberance in the southwest - so what does it mean for the compatibility of our dreams and beliefs?
Most citizen science has citizens collect data, which is then analyzed back at the ivory tower. How can citizen scientists analyze data, too? Say, how can parents in my math clubs compare notes on how they help their five-year-olds with scavenger hunts for nonlinear functions? One parent helps by providing examples, another by asking questions, another by dispersing hugs. Different footprints; how can people analyze results together?