Are today's children consuming a healthy, balanced "media diet"?

I was reading the paper a few weeks ago and as the father of two teenagers was blown away by the following study:
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The average young American now spends practically every waking minute -- except for the time in school -- using a smart phone, computer, television or other electronic device, according to a new study from the Kaiser Family Foundation.

Those ages 8 to 18 spend more than seven and a half hours a day with such devices, compared with less than six and a half hours five years ago, when the study was last conducted. And that does not count the hour and a half that youths spend texting, or the half-hour they talk on their cellphones.
http://www.nytimes.com/2010/01/20/education/20wired.html