There's no reason why an Xbox that can't play used games is not acceptable, but a PC that can't play used games due to CD keys is. There's no reason why on-the-disc DLC is not acceptable, but the same content when actually downloaded is. There's no reason why offering extra quests to Kingdoms of Amalur: Reckoning preorders is not acceptable, but offering in-game items as preorder incentives is. There's no reason why DRM is not acceptable, but Steam is.
While we may muster outrage for all of these things when we feel they go too far, the fact that we've permitted them in any form is evidence of a fight for consumer rights that has already been lost.
At this point, the reaction these schemes get is simply a function of how skillfully the publishers present their plans to the public. If they can just find the right combination of words in the right order, people will accept them without protest. But if they botch the marketing message and gamers get the sense that they're entitled to something the publisher is taking away, they wind up with a furious fan base promising to cancel preorders or buy the competition's product to make a statement.
No doubt, some of those angry gamers follow through on their promises. But if you look at the bigger picture, that outrage isn't widespread or deeply felt enough to make these sorts of schemes unprofitable. And because of that, publishers will keep resorting to them whenever possible.
It's not that publishers are evil and have a master plan to take away consumer rights. It's that taking away consumer rights is a side effect of their actual goal here, which is to have control over their product. It's a tug of war, and there's no way for the publishers to gain ground without taking it away from their own customers. They can't use always-on DRM without limiting our ability to play a game without an online connection. They can't curb used sales without impacting our ability to resell our own games. They can't stop piracy without stopping our ability to install a game on any computer we feel like.
Unfortunately, the digital era is giving publishers more ways to control their products than ever before. Between DRM, end-user license agreements, online pass schemes, and virtual goods, we own less of our games than ever before. And as much as we might lash out and complain about the constraints imposed upon content, we're basically arguing about semantics at this point.
So we can rail against these tactics all we want, writing angry petitions, message board posts, and editorials about the subject, but the bulk of us have already accepted them in some form. Now it's just a matter of time before publishers figure out the least offensive way to communicate their restrictions to the masses and enough people get on board. Whatever consumer rights previously existed in gaming, they have been significantly and permanently curtailed, and it has happened with our own tacit approval.