Writing to iCloud? Is it doable from a wifi rev2?

I think it would be fun to have a wifi enabled device write data to a file I have stored on iCloud. Is this possible, has anyone done it and would share their code with the rest of us?

I am using ThingsSpeak now, but this may or may not always be possible in the future, they may implement limits etc., and a file on iCloud presumably has no such restrictions.