"The biggest threat is internal."
This is one of the great truths of the software industry from my perspective:
At a corporate level, history says that leaders in their markets are almost always knocked off their leadership position by their own actions and not by actions of others. If you look at the press coverage it’s all focused on external threats but the biggest threat is internal, and it’s not just true of Google, by the way.
http://money.cnn.com/2008/05/13/technology/lashinsky_schmidt.fortune/index.htm?section=money_latest