We can't keep people informed. At best we can make information available. The full information might exist in a distributed way and even an integrated way - but never as a whole and complete. A posted mission statement has not proved itself in any company I've heard about nor been in. Occasionally, it might have helped.
People can have a voice, too.
They need that. Human beings are terrible at listening. The Pushers are not eager and open listeners to what the Pullers are saying. Maybe it isn't alignment of goals that we need nearly som much as alignment of mechanisms and lots of communication. My own experience in interviews and in workshops large or small is that there is incredible alignment but that people don't know it.