It depends on the company. I set up a wiki for a small company of all fairly technical people. It turned out as a great place to share ideas and documentation. Of course it was a small group of people, but if the people using it respect each other then I don't see a problem with the openness of allowing most everyone to edit things.
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My last 2 companies have used Jabber as an internal chat server, other than cases like that most people are using AIM or MSN it seems.
It depends on the company. I set up a wiki for a small company of all fairly technical people. It turned out as a great place to share ideas and documentation. Of course it was a small group of people, but if the people using it respect each other then I don't see a problem with the openness of allowing most everyone to edit things.