I don't think voice chatting with strangers is as dangerous as the addictive nature of the video games themselves.
Voice chatting with strangers, who are also addicted to these video games, doesn't put kids in danger the say face book stalkers with fake photos put kids in danger.
I had a son who was addicted to World of Warcraft, and knew of other boys who were also addicted. It's a true addiction - in that, it creates craving and panic, and changes brain structure. That summer my son (who was 16 at the time) could only play games or sleep. If he was off the game for any length of time, he was asleep.
My other son had a friend who became addicted to WOW and the parents of this boy would arrange times for his circle of friends to come "kidnap" him - they'd help drag this boy out of the house and pay for the group activities - kayaking, pizza, whatever, to get this child OUT of the house and off the computer. If he wasn't physically dragged away he wouldn't leave.
Yes their game-play time just keeps on increasing day after day. I will make sure to start putting time limits on heir game play.
In regards to the voice chat, I have been reading may articles that talk about bullying in these games. I guess the worry is that Im not sure if any cyberbullying is happening in these game spaces - if my son and his friends are doing any of the bullying and vice versa. The people that they chat with in these games are from different age groups and I dont know if any of the older players in age use inappropriate language with my son while they play WoW.