http://www.bbc.co.uk/blogs/technology/2008/02/playstation_bounces_back.html To sign a NDA it must be something huge in Sony's eyes.
learning from the cloverfield people. don't let anyone know what it is and you spark their curiosity.
NDA's are commonplace in business, including the gaming industry. Nothing new there. The fact that they show it to a reporter and won't let him write about it just means it's really early in development and they don't want anyone writing about all the glitches and what have you.