Nicholas Carr is a good introduction, but he just touches the surface of this sort of thinking. A lot of his thought is like a popular version of stuff by Neil Postman and Albert Borgmann, though I'm not actually sure how much he's been directly influenced by them. To be fair, most of their work was done before the internet became widespread, so Carr's exploration of the online aspect of the impact of technology is quite welcome, but I think it also may lead some people to think that it's a problem unique to the internet, which is unfortunate. The internet is just a specific case where the issues are more pronounced, but all of these sorts of criticisms are really getting at the sort of thing warned against by Brave New World. There are those of us who think that we're rushing headlong towards the scenario that Huxley depicted because we're so freaked out by 1984 and the like that we're blinded to other, more insidious threats. Incidentally, a lot of these sorts of criticisms all trace back to Heidegger's thought. If you've got a solid foundation in philosophy, "The Question Concerning Technology" is a fascinating read.

P.S. I apologize if anyone finds this post a little too esoteric or off-topic. I just have strong feelings about the way technology is used; I think that those who work to advance technology need to have a good understanding of the ethical considerations related to their work, and that most of the time this is lacking.