With ADD medicine becoming more and more pervalent in American colleges- is that proof that kids' brains are already rewired? and society is forcing them to snap back to the old way of thinking?
There isn't any evidence that I'm aware of that there has been any noticeable change in people's abilities to do actual, focused work: studies today show that most people can at most manage around 4-5 hours of focused work, and as far as I know that hasn't changed much in the last 200+ years. Ritalin can allow a healthy person to put in bursts of 10+ hours of focused work. Of course students are going to take advantage of that. My understanding is that it's also fairly common in other high pressure situations that require prolonged focus (stock trading, etc.).
Things like the web/etc. do allow people to do more multitasking-esque behaviors (with the obvious impacts on focus), but that's less about people's brains being rewired at some fundamental level and more that there are now more opportunities to goof off. Pre-internet, you had a much higher activation energy of chatting with friends (you had to go call them and talk with them, versus clicking three times to get to Facebook). I don't think that's limited to people in the younger generation, though: one of my family members (an English professor, one of the top in her field in the world) will sometimes turn off the internet/block distracting sites while writing and does all of her editing away from the computer in order to avoid Facebook/reading the news/playing scrabble against the computer.