You're only looking at half of the value, though. It's because it has value to others that it's worth keeping the secret. I'm asserting that the normal case is for the value to others to outweigh the individual's value. You are correct that it's asymmetric, of course. And yes, zero sum games would tend to be something of a limiting case. I'm not sure you can find a negative sum game for society as a whole, though you can for some particular group.