This article was a bit misleading... People who read the linked BusinessWeek article would've found that EA was *NOT* demanding a cut from every second-hand sale; I think they know well enough that such is a violation of US copyright law. (people have mentioned Vernor v. Autodesk; various other cases have stated the same thing for over 100 years now)
What *IS* going on here is that when you normally buy a used disc, you just get the base game; if there was DLC with it, you don't get it, because it's not physical. EA's trying to offer a "package," where they let you basically buy DLC "used" for $10US. So if the previous owner had, say, purchased The Sims 3 new, and had $100US worth of DLC expansions, EA will allow you to buy that $100US worth they had for $10US.
It's an interesting move, I'll say. Running it won't be that hard; their own online stores track CD keys used with their DLC, so they just check the new owner's CD key to see what DLC was previously used with it. It's also a bit shrewd: they recognize that used-game buyers are likely stingier with their money, so basically offering them a "discount" on DLC could be the right way to boost DLC sales. Of course, there's also some unnecessary complication there, in that someone buying a used game might not know what DLC they'd be able to get for the reduced price, if any. So how well this works out will remain to be seen.