I've always loved this book by Andy Grove of Intel. Just seeing the title on the bookshelf in my office has often caused me to reflect on things, take my blinders off, and build contingencies.
I just read an article in Fortune on "(Bill) Gates' Golden Rules." One really struck me: Institutionalize Paranoia. Ray Ozzie is quoted, "Bill and Steve created what I guess I'd characterize as a culture of crisis. There's always someone who's going to take the company down. It's mythical, but at any given point in time, there might be two or three big competitive things that the company is juggling. It's something people here are used to, and it's accretive in terms of making things more resilient over time."
The notion of an institutionalized culture of crisis making people and organizations more resilient is very powerful. We have seen too many organizations/people become complacent. Many complacent in their success. Others just satisfied to muddle along. Others oblivious or blaming others.
As I reflect, most of the high performance organizations I have been involved in have a healthy sense of paranoia or crisis. It seems to keep the creativity high, the energy and activity levels high and drive performance.
As with anything, anything taken to excess can be destructive. There are many examples of taking the notion of paranoia too far. Those that don't like the concept of institutionalized crisis will pull out those examples to refute the idea. Many will undoubtedly use Microsoft itself as a prime example of things gone wild.
With all that taken into consideration, I will generally side with the Paranoid.
Finally, I remember someone telling me, just because you are paranoid, doesn't mean something isn't out to get you!