Yeah, I like this idea, in case of NDA, we should create a 'Beta Testers' subforum, with restricted access, given only to members who were proven to be testers, just like the green room ('the what?' room I hear certain members ask :p)
I really don't want to have to migrate to another forum just to discuss the beta, considering that the official forums, and its member-base aren't my cup of tea (I just congratulated myself for not swearing there...) and we know that the devs and the excellent PR team check here anyway. (Lee has tipped his hat to us enough, we should return the favour!)
One thing you'd have to do though, is to disable image tags in that forum. I remember in the APB beta the dev-team and moderators were very strict about images being uploaded to free-access sites like photobucket, as people could just view material that was supposed to be NDA protected. Because of that, photos would have to be attached to posts.
Also, I think that infractions and temporary bans from the beta section should be made for people in breach of NDA.