My sense is that the way adolescent society has evolved in recent years has increased the potential for this kind of isolation. We have given teens more money, so they can construct their own social and material worlds more easily. We have given them more time to spend among themselves--and less time in the company of adults. We have given them email and beepers and, most of all, cellular phones, so that they can fill in all the dead spots in their day--dead spots that might once have been filled with the voices of adults--with the voices of their peers. That is a world ruled by the logic of word of mouth, by the contagious messages that teens pass among themselves.
Recommended reading to anyone interested in ideas, epidemics, marketing, culture, television, personalities and many other topics. Excellent book--can't wait to read Blink--The Power of Thinking Without Thinking. You can also check out other Gladwell writings on his webpage.