I see two sides of a coin in many arguments presented in this thread...

I think this goes very deep to the core.. if being more open creates more expectations, which often leads to let-downs and dissatisfied customers (generally people don't have the nerves to stand the many delays and changes to the product [which can be HUGE], and those happen all the time, especially in startups) and often involves many problems to companies business-wise, versus not being open which closes the possibility of community involvement in projects, not to mention a more or less disgruntled community... I bet finding the balance between the two isn't the easiest thing to do... to be as open as possible without damaging your company in the process.

EDIT: I felt I should add that there are probably much more to the issue than the things I just said; I have that unfortunate characteristic of talking about things I'm not entirely familiar with.