The allure of Secret is that you know that a given secret is from someone you know. Diluting the pool is harmful to that message. What they could do instead i

The allure of Secret is that you know that a given secret is from someone you know. Diluting the pool is harmful to that message. What they could do instead is only share secrets if you have N contacts in common. This solves the bot problem - the target will not add the bots. You could also have some sort of threshold before showing secrets as well. That said, I've never used Secret so this may or may not work. It'd be interesting to play with the Secret data to see how the social circles overlap and what kind of traffic patterns they see.