Finally, before we say goodbye to this very interesting topic (see the two posts below, latecomers): Numerous surveys and studies have shown that parents tend to vastly underestimate the amount of time their own children spend on the computer and in front of the TV, and how much violence they are exposed to onscreen.
If you think your child spends "hardly any time online" and "doesn't watch much TV", look again. Be honest with yourself, and as so many readers have advised, keep the lines of communication open. Both ways!
Thanks for being so involved here, guys. Let's keep this going in comments as long as new information and ideas turn up. And now, back to your regular scheduled programming!