I believe we will not have to wait too long to see unanticipated effects on civilization from the internet. Think of what it is. A billion people all over the globe in instant communication with an enormous store of information at their fingertips. Collaboration by scholars and terrorists is something we are currently familiar with. But what will be the effect of many groups of like mind on subjects in financial, religious, political, scientific or artistic areas being able to seek each other out and collaborate in real time. One thing that protects us from the nuts in our midst is that they are dispersed. On the internet, they are no longer dispersed. They only have to find one another. On the positive side, geniuses will find one another. It is actually going on now, but I am wondering what the effect will be over decades. If you have a niche itch, you can find a friend to scratch it in Cairo or Sydney. 
I would not give much credibility to anyone who claimed to know the long range ramifications of such an unprecedented phenomenon. I cannot see anything in history to draw on. Books, mail, telephone, radio and TV were primitive by comparison.