It depends on who the ad is being served by.
All DiS’ ads come through W00t who are like a broker that are selling Sean’s ad space for him. Some of it goes to people who want to specifically target DiS, but most is effectively resold to other ad companies on the fly when W00t don’t have specific campaigns like that to fill the space with.
When you see the adchoices bit, the ad is coming from an ad programme that’s signed up to voluntary self-regulation (usually Google Adsense, but it could be elsewhere). If that’s not on the ad, then it’s coming from one of the other programmes that hasn’t signed up to that. And as it’s a voluntary programme, dodgy advertisers are more likely to buy their advertising space through a platform that doesn’t offer the adchoices functionality.