Wow, I'm coming to Apple's defense. What has this forum come to?

Some of you keep saying this is an oversight from a normally detail-focused Apple. I say that it's completely intentional.

This is really a difference in spatial reasoning. For you, it makes more sense for the functions to change based on orientation, You're relating the buttons to the area outside the device as well as the what's happening on the screen. But you seem to be assuming that everyone thinks this way, and that's not the case. The rest of us (and I'm assuming I'm not alone) prefer to relate the position of the buttons with the frame of the device. That way I always know that the same button will do the same thing in every position. That makes more sense to me.

So either way, there will be a group of people who are unhappy with the way it works. However, I wouldn't be surprised if Apple indeed tested changing the volume buttons with a change in orientation, and determined that it would just be too confusing for enough people, and that simpler was better in the long run. And before you say it: no, I'm not implying they used focus groups. Thankfully they don't!