Powerful people often act as if the rules don't apply to them, or that even if the rules do apply, they don't really care.
Research shows that when people feel powerful, they are more likely to act according to their own goals, rather than what's best for the group. They are less sensitive to what's happening around them, disregard input from others, and ignore social norms. They are more sensitive to their own internal states and feelings, and care less about what others may think of them.
(And this happens even when the experience of power is new or temporary—there's something about power that seems to immediately turn our vision inward).
The net result is a lot of bad behavior—not necessarily illegal, but certainly obnoxious. Powerful people are apt do all sorts of socially inappropriate things. They interrupt more frequently, invade personal space, take credit for other people's ideas, make insulting remarks, and are more likely to engage in sexual harassment (okay, that last one actually is illegal).
One study even showed that powerful people are more likely eat with their mouths open. I had noticed that one myself in graduate school. It often seemed like the more prominent and well-regarded a professor was, the more unpleasant he was to share a meal with.
One of the great ironies of all this bad behavior is that while we may find it personally offensive, breaking the rules of good conduct actually makes these people seem even more powerful.
New research from psychologists at the University of Amsterdam shows that when someone violates a social norm, we assume, often unconsciously, that they are somehow free to do what they want. In their studies, men and women who took someone else's coffee, brushed minor mistakes under the carpet rather than correcting them, put their feet up on the table, or flicked cigarette ashes on the floor, we judged as more powerful than those who were better-behaved.
Despite being seen as rude and somewhat unpleasant, the rule-breakers were seen as more influential, more likely to hold a leadership position, and more able to "make life difficult for others."
I hate to be an advocate for bad manners, but since so much of any individual's success depends on how they are perceived, it's worth taking a moment to think about how a little strategically bad behavior might raise your profile. Eccentric is better than offensive, because eccentricity is about breaking the rules in relatively harmless ways, and keeps ill will to a minimum.
Being able to project an air of indifference, to make it seem like you don't really care what other people think (even if you really do) and are free to do whatever you want, will leave others with the impression that you are a force to be reckoned with. Just do yourself a favor, and however you decide to break the rules, keep it legal. And seriously, don't chew with your mouth open.