And then their local system gets coffee spilled on it and is friend, and they call you asking where their data went... I totally understand not wanting to be r

And then their local system gets coffee spilled on it and is friend, and they call you asking where their data went... I totally understand not wanting to be responsible for their data, but you'd better be really sure that they understand how things work. Uploading to a web app makes people think their data is in the cloud. If you want their data saved locally, use a native UI that makes it clear they are saving a file to their system.