amistill, I am sure you didn't mean to come across quite so judgemental and patronising. 
Thrifty, I agree with Ellen. If my ds starts taking the proverbial P with computer time his consequences is losing access for a pre-agreed amount of time.
Like your ds, taking away all screen time completely would be as much of a punishment for the rest of the family as it is for ds - although I have had to resort to that on a couple of occasions - so we have degrees of removal, iyswim.
He is currently totally obsessed with Minecraft and been given access to our old MacBook for playing it, for a pre-agreed amount of time per day. When he first started he was allowed to play on it for the whole of his 'computer time' but we found this fuelled the obsession massively and his behaviour deteriorated as well, so now he can have half an hour on that and the rest of his computer time on his DS.
He knows the rules and the consequences, but has several times wangled it so that he's been on it for an hour while I was busy and didn't realise. (My fault but he knew what he was doing.) On those occasions he has his laptop rights removed for the rest of the week - no arguments. If we stopped all computer time, as I said, it would be punishing the rest of the family as much as him, so he is still allowed to go on his DS, with the half an hour laptop time removed and gets his 'gaming-fix' that way instead. I think we've had to do this twice now and he knows it will happen, yet he still did it again last night.
I had a visitor, so told the boys to have computer time upstairs. An hour later ds2 came down in tears to tell me ds1 had been on the laptop for an hour and wouldn't let him have his hour on minecraft. Interesting discussion with ds1 ensued, while he tried to tell me that last time this visitor came they had an hour each - I have a terrible memory and he could be right, as it was the school holidays and prior to the half-hour restriction being imposed - but he knows the rules now and that he is only allowed half and hour and he broke the rule, so has to accept the consequences. (This is hard for him to take, because he is rules/routine led, so in his mind what happened the previous time that particular visitor came over-rode the current rules.) Needless to say he was not at all happy and we will have it all over again tonight when he gets home and wants to go on the laptop and I have to reiterate the consequences of his behaviour.
Prior to this system - before Christmas - he was getting increasingly shirty and demandng about having laptop access to go on various things and his behaviour was unacceptable as a result. We maintain that the laptops are dh's and mine and we are kind enough to allow him access to them - on our terms, not his, but he was becoming increasingly demanding and petulant about it and tantrumming if we said no. So, we removed all access to laptops for the whole of December. He retained his 'computer time' because he was still allowed on his DS, so despite him being thoroughly cheesed off with not being allowed on the laptop, we still had an hour and a half of peace every day! 
As Ellen said, removal of Xbox live for a determined amount of time, as a consequence would still leave him access to standard Xbox games, so he wouldn't be completely bereft of gaming, but would send the message that if he abuses a privilege that you have been generous to allow him, then he loses that particular privilege. Perhaps a three strikes and you're out type idea might also work, so, say you have to remove Xbox live access for a week three times then he loses it for a month.
I also agree with the suggestions to look at the Teens board and also what Polter said about your dh needing to take more responsibility for not leaving your ds wide open to temptation that he clearly can't resist at this stage of his development.