I worked in a similar environment once (Large government contractor on a NASA program). There was lots of cube-walking, and generally, it is a distraction. BUT- You know that when you walk into someone's cube to ask them a question, it will be a bit of a distraction and it takes a little effort, so you make sure you need to before you do. Similarly, when someone walks into your cube, you know they think it is more important than something that would have been sent via email.

Not that it works perfectly, but the default of dumping everything into email is a problem. There are several other, possibly more appropriate methods of communication (phone, in person, waiting until the status meeting, break room chat, lunchtime chat, etc). Email is just the easiest and therefore most likely to be abused.