Frontline recently aired a documentary called Digital Nation which took a look at all the different ways we use media.  And at recent research in the field.  One of the scientists they interviewed is Dr Gary Small at UCLA.  He looked at people’s brains while they read a book, and other people’s brain while they used Google; there was a two fold increase on the extent of activity while interacting with Google. Primarily, in the frontal lobe where most of our cognitive processing goes on .
They also filmed South Korea where many teenagers are addicted to video games.  Here they have  legendary internet cafes and the gaming craze is out of hand.  A few people have even died after gaming marathons for many days without food.  A Korean psychologist did research showing how addictive it is and now they treat this as a psychiatric disorder.  They are also now requiring  media literacy by 2nd grade, to promote healthy internet habits.