Which way is up or down? why does the pole change places?

Question

Now and again the two poles change place! During the course of the last 5 million years this has happened around 25 times. Approximately 720,000 years have passed sine the poles last changed around and the phenomenon will certainly repeat itself, we just don’t know when. The dynamo in the Earth’s interior is unstable such that on occasion the field weakens, loses its bipolar character and regenerates with reversed polarity. It is believed that the reversal process takes several thousand years, but some modern opinions suggest a shorter time. We can only imagine the confusion when the compasses of the world suddenly turn a half circle! Does it effect the planet in any way? if so, how?

Answer 1

There will be no confusion. Almost no one, other than those too cheap to buy a GPS, are using magnetic compasses, because they're too inaccurate for modern navigation.

Ships and planes use gyrocompasses or GPS/inertial nav systems, and navigate to true north, not magnetic north.
http://en.wikipedia.org/wiki/Gyrocompass
http://en.wikipedia.org/wiki/Gps
http://en.wikipedia.org/wiki/Inertial_navigation

Answer 2

The magnetic shield that is formed by the core will be diminished, or non-existent, allowing more radiation to reach Earth's surface from the sun and cosmic sources... likely, cancer rates will rise in humans, and some species may go extinct because of their sudden 'lack of direction'.