In a bit of tragic videogame-related news, five boys aged 13 to 16 have been arrested in Latvia for the murder of one of their friends. The boys apparently beat the 16-year old victim to death using moves and techniques emulated from Mortal Kombat. Now, the Latvian authorities aren't wholly blaming videogames, citing also violence on TV and movies, and of course the suspects probably had their reasons for the heinous act.
Anyway, I've always heard stories about little kids doing 'Hadokens' and Dragon Punches in play, sometimes getting hurt in the process. It's a parent's responsibility to keep an eye on their kids, not particularly to focus on videogames, but on their kids' behavior and upbringing in general.