Second, it's not even the noise that wrecks people but visibility from behind ("open-back visibility"). That's not because people are constantly hiding things. It suggests low status and makes it hard (and stressful) to perform at one's best.
There are environments where open-plan offices are better, but they're rare. One is a trading floor, where seconds matter (a lot) and information must be broadcast quickly and verbally (i.e. yelling). Unless there's a real-time sensitivity to what they're doing, programmers are better off with more privacy.
If you are going to use an open-plan office, the least you can do is to give everyone a 7-foot wall at his or her back.