We also use component local state for things like that, and David Nolen (Om) likes component local state too. But the state goes up top by default. The biggest reason for this is because you might want to attach a diagnostic component to your state (e.g. a json editor [1]), and you don't want to have to change the shape of your state to do that.

[1] https://github.com/dustingetz/react-json-editor