How about having a developer area that is treated like a library? Silence enforced at all times, you have to whisper if you strike an impromptu conversation. And if that bubbles to a brainstorm, get up and grab a conference room to talk about it.
I've thought about this too, but my suspicion is there are some good reasons why more companies don't do this. Anybody care to chime in?
A practical concern might be that a library needs a librarian to shush people. And it needs people to obey the librarian when they do that.