I love the idea of touch ID but I envisioned not having to type a password anymore. I don't buy apps every day but maybe once a week I will buy something that requires a password. It seems that about half of the time it makes me enter a password and the other half of the time I can authenticate with my fingerprint. Why is this? Is it normal behavior? And how does Apple decide if I need to enter my password or fingerprint when I go to download an app? It seems fairly random.