I see from the docs that this plugin modifies the current requirejs.config (if present) and tries to be non-destructive about how it does that. This means, amongst other things, that if you remove a package from bower, it won't be removed from the config.
Can I suggest a different approach: modify a separate config that the user then overrides.
var autoConfig = {
paths: {
// This always maps directly to whatever
// components are installed via bower.
}
}
require.config(extend(autoConfig, {
// My rules go here.
}));
This ways it's obvious what grunt is in control of and what I the developer am in control of.