Having a 4MP digital camera is a boon in some ways. On an average, I have noted that the size of a 4MP photograph is between 500K to 1.5M. If we move to an 18MP camera, the size becomes 5MB for JPG/JPEG. If we use RAW, the size becomes 25M.
So, while the rise in mega pixels is great for camera manufacturers, the hard drive industry will also benefit from this insatiable hunger for space.