Do I need to let a wine "breathe," or does oxygen make it spoil?

Hello there! I'm Dr. Vinifera, but you can call me Vinny. Ask me your toughest wine questions, from the fine points of etiquette to the science of winemaking. And don't worry, I'm no wine snob—you can also ask me those "dumb questions" you're too embarrased to ask your wine geek friends! I hope you find my answers educational, empowering and even amusing. And don't forget to check out my most asked questions and my full archives for all my Q&A classics.
Dear Dr. Vinny,
I have been asked to try out a new product designed to preserve wine. It is an ingenious way of allowing wine out of the bottle while the air going into the bottle fills a displacement bladder, thus keeping the air away from the wine and therefore keeping it from spoiling. The problem I have is that this seems contradictory to the advice of letting a wine breathe, or decanting, where oxygen is encouraged to get into the wine. Am I missing the point?
—Rich, Camden, N.J.
Dear Rich,
Sometimes oxygen is desirable and sometimes it's not. After you open a bottle, you may want to help the wine "breathe" by swirling it in the glass or decanting it to expose it to oxygen, which will help develop the bouquet, soften the taste and let the wine open up. But when you're trying to preserve wine, a copious amount of oxygen is something you want to avoid. If you can't finish a bottle and want to return to it later, then you're back to trying to find ways to eliminate the oxygen so the wine doesn't oxidize too much. The bladder gizmo may come in handy for that.
—Dr. Vinny