Power really does go to one's head, and in a fascinating August 14, 2010, Wall Street Journal story, "The Power Trip," Jonah Lehrer turns to sociologists, psychologists, and neuroscientists to explain how and why people change when they attain power:

From prostitution scandals to corruption allegations to the steady drumbeat of charges against corporate executives and world-class athletes, it seems that the headlines are filled with the latest misstep of someone in a position of power. This isn't just anecdotal: Surveys of organizations find that the vast majority of rude and inappropriate behaviors, such as the shouting of profanities, come from the offices of those with the most authority.

Psychologists refer to this as the paradox of power. The very traits that helped leaders accumulate control in the first place all but disappear once they rise to power. Instead of being polite, honest and outgoing, they become impulsive, reckless and rude.

There's some good news: Being considerate and agreeable seems to result in people trusting you with power; being a Machiavellian manipulator does not. Nice guys finish first. But what happens to that nice guy when he finishes first?

While a little compassion might help us climb the social ladder, once we're at the top we end up morphing into a very different kind of beast.

"It's an incredibly consistent effect," Mr. Keltner says. "When you give people power, they basically start acting like fools. They flirt inappropriately, tease in a hostile fashion, and become totally impulsive." Mr. Keltner compares the feeling of power to brain damage, noting that people with lots of authority tend to behave like neurological patients with a damaged orbito-frontal lobe, a brain area that's crucial for empathy and decision-making. Even the most virtuous people can be undone by the corner office. 

Lehrer provides descriptions of studies and experiments that bear out this change -- how the powerful respond to conflicting information, how they deal with their own ethical lapses vs. those of others, the impact of social isolation on the powerful.