Create a peer-to-peer platform for collaboration. Instead of a central repository like a wiki (e.g., Wikipedia) or Github, everyone owns a master copy, and the software automatically pulls updates from everyone else's copy to keep things in sync, and makes sure everyone has the most up to date version.
We envision a filesystem interface, so a distributed network filesystem, though probably many other architectures are possible. Data contention, e.g., merge conflicts, could be handled by the system (maybe locks), higher level tools (maybe storage consists only of messages written in order, never modifying or deleting anything old), or social engineering (they have agreed to collaborate so aren't going to be evil to each other, which is the source of difficult merges).
This might be especially useful for collaboration with large amounts of data, e.g., video, where centralized hosting might be expensive. However peer-to-peer collaboration with large data will require everyone have high bandwidth and large local storage.
Peer-to-peer synchronization should be encrypted to thwart outsiders from eavesdropping on the collaboration. Of course authentication also.