Jonah Lehrer may have figured out why so many powerful people seem to act so hypocritically.
In his excellent blog, "The Frontal Cortex," he suggests it may be because "power makes us less sensitive to the needs and feelings of others - it silences our empathy - and so we only think about our own motivations and needs."
Social scientists have long suspected that our our sense of fairness is rooted in feelings of empathy. (I personally think it's the other way around, but in any case, it seems logical that people who are isolated from others because of their "special status" would be less able to put themselves in their place.)
Seen that way, Scott Brown's pickup is a graphic way to signal that he has the same tastes and interests as his constituents. And it may also explain why President Obama tends to drop his "g's" when speaking at large rallies, even if they're on his teleprompter.