Add the ability for numerous organizations to support a single event. And for organizations to have matching events (i.e. same event but each has it at their location).
Each signup is owned by the organization that brought that user. But aggregate statistics are available to all organizations.
So... what should be kept as the property of each organization and what should be shared?
And keep in mind that Ohana can be the honest broker in this case. Ohana will know all users who have signed up, but it can limit what each organization knows to their specific users and the total number signed up. So organizations won't have to worry about poaching.