The ability to set capacity caps for a given folder via the API would, I'm sure, a very highly sought after feature. Use Case: (hypothetical) I have a dedicated server which I use for backup storage -- a friend would like to use my online storage server as well. I agree, but I'd only like him/her to use a maximum of 1GB of storage space. Using the API, I should be able to set any given folder which is attached to his specific secret key, an (admin) set maximum storage value. This is a highly useful feature when thought about at length.