Based on Google's culture (or what I have heard about it), I don't think this is surprising.

It also lets her get introduced to the people at Yahoo! who have ideas, those that are still passionate about the company, and those that will make a difference.

The only reason this isn't surprising is that every new executive in the history of business has proclaimed an open door policy. Email would be far more efficient to deliver and review ideas on their merits. Open door is more about gauging the political climate and finding out who will be a follower from the get-go, who is star struck, etc.

And then they go on to put secretaries in the room in front of the open door to stop people from going through the doorway.

I once happened to walk past the open door to the office of the Director of the CIA. I briefly considered walking in to say, "Hi," but then I thought better of it.

IIRC, Scott Thompson had an open-door policy as well. I remember because in the leaked email he mentioned it after acknowledging layoffs.

Such offers tend to be self-limiting, though. Most people will know whether they are really welcome.