How should we treat questions that break NDA? For instance: questions about Mac OS X Lion. Should we close them? Or just leave them be?
I can't see any reason to allow NDA questions in this case.
I am more sympathetic on Stack Overflow where developers are working with final (but unreleased to end users) APIs that they need assistance with.
For consumer facing things like an OS, Software, Hardware, etc.. I see no benefit to allowing private NDA questions, since things may change before final release to consumers.