James Shelley thinks the medium not only changes how we read, but alters how our brains function:
So here is our trajectory: more text, faster, in smaller chunks. If we use technology that forces us to think in 140 character bites, that is exactly how the brain will adapt. If we use technology that forces us to skim-read tomes of information, that is exactly how the brain will adapt. If we use technology that wires our consciousness to a global network during ever waking moment, that is exactly how our brains will adapt.
(Via Pat Dryburgh.)