Scott Aaronson has some good posts on the matter: http://www.scottaaronson.com/blog/?p=122 http://www.scottaaronson.com/blog/?p=122 http://www.scottaaronson.co

Scott Aaronson has some good posts on the matter: http://www.scottaaronson.com/blog/?p=122 http://www.scottaaronson.com/blog/?p=122 http://www.scottaaronson.com/blog/?p=1720 http://www.scottaaronson.com/blog/?p=1720 (The second of these talks a lot about the matter of the boundary that you mention.)