I suppose there is a small gyro in the camera so it knows which way you're holding it and it rotates the file appropriately, but I'll say that very likely the spots will appear on the top if you hold it the "typical way" with the shutter button rotated up and your right hand over the camera.
A gyro would add a few K to the cost of a camera, not to mention that a gyro system wouldn't work on a camera anyway -- well, you could make it work, but first it would take a couple minutes to complete gyrocompassing and then compute local level. A gyro is an inertial instrument so it must keep track of latitude so that it can constantly update local level as the earth rotates.
The camera uses something that is very effective and cheap to handle orientation -- a simple switch operated by a pendulous weight. That is why the camera gets confused and doesn't know if it is in portrait or landscape mode when pointed towards the zenith or when pointed nearly straight down.