Remember kids... always wear a helmet. (The almighty bikeradar helmet thread)

Never worked out whether the politicians are all that way before they enter politics or something changes once they are there.

Six of one and half a dozen of the other. You pretty much have to be an egomaniac to stand for political office, but there is clear evidence that people become increasingly deranged with time in power. To take just one recent example, it took A.Blair a decade to transform from well meaning idiot to genocidal psychopath*.