The snapshot is not so random. I can set the trigger to 'motion' and save. From the myDLink lite app, I will turn on motion detection and then turn off motion detection. When I go back into advanced settings, it has changed the trigger in snapshot from 'motion' to 'always'.
This doesn't seem to occur when I turn on motion detection from the mydlink.com.
So, in conclusion, the current myDLink lite app changes the snapshot trigger to 'always'.