I think it takes a different attitude to show us the inside, inside the 'sausage factory' so to say.
The following from the Twitter engineering teams illustrates what I mean
http://engineering.twitter.com/2011/04/twitter-search-is-now-3x-faster_1656.html
Admit it, it's probably unlikely that the product - no matter how well engineered - accounts for the valuation of technology firms. You might as well be 'open' because people leave, they talk in pubs, share their war stories with college mates. Your big secret isn't going to stay secret for long (shades of Wikileaks). By way of explaining why I think it is good for corporations to be 'open', consider the good of this reflection on the dev history of a service: The Evolution of the Flickr Architecture http://t.co/lDZdgn0.
What is lost by making this information public?