I don't see how my example above is any less relevant if the event is less mainstream. Ultimately, users want to publish their plans where most of their friend

I don't see how my example above is any less relevant if the event is less mainstream. Ultimately, users want to publish their plans where most of their friends will see them. That is Facebook. Ever think about putting the app on FB, vs. rolling your own? You, sir, have a chicken and egg problem.