The Sierra Club initiated an effort that was adopted by an environmental organization in New Mexico to tax video games in an effort to encourage kids to spend time in the outdoors.
I'm skeptical that a nominal excise tax would be punitive enough to discourage a purchase and suddenly encourage playing outdoors. However, perhaps with increased revenue one of these organizations might have the funds to be able to reach out and market to these children to encourage them to get outside.
I think the responsibility lies with the parents, not the IRS, to pull the power on the xbox and encourage their kids into the wilderness.
I say it is the parents who need to do it. Video games are not the evil, rather it could be TV, movies, toys or whatever a kid likes to do that keeps them from running around. I let Ford take his Nintendo DS Lite with him on backpacking trips and play it in camp. I figure the kid earned it after hiking all day 😉