There are only two reasons it would need to be private:
(1) you're collecting data where if it was public, people would be outraged. That's spying.
(2) you believe the data is anonymous and valuable, but only you / your group should benefit from the insights it provides. You're afraid someone else is going to 'take your ideas' and execute them better than you can.
Point 1 is ethically wrong, in my view. Point 2 is not ethically wrong, but IMO means what you are just trying to run a monopoly on an idea. That's fine, people do it all the time, especially companies - but I think this is wrong for the progress of humanity overall and I dislike it.