Wikipedia has a useful table in its article on income tax in the United States:
There's a lot of information in this table, not much of it obviously assimilated into any argument, but I want to make one point: top tax rates used to be a lot higher.
This blog post for The Atlantic debates whether Obama is a "transformational" president in the way Reagan was when he ended the New Deal era of American politics. I don't know the answer to that, obviously, but it seems clear that if he is, we will see a return to higher tax rates. The New Deal era, from FDR's election in 1932 to Reagan's election in 1980, featured an incredibly high rate of taxation. During Reagan's term in office those tax rates were brought way down. The tax rates under FDR and all presidents to Reagan were high because they had to be--huge wars were fought, entitlement programs were invented, and the role of the federal government vastly expanded.
I am not well educated on the social history of the U.S. in this "New Deal" era. But I'll speculate that taxation was viewed, much more than now, as an important civic duty. Especially during war time. For example, FDR levelled a "victory tax" on all incomes over $624 in the U.S. in 1942. Even for citizens who couldn't, or wouldn't, fight, they could be an important part of the war effort by paying their taxes.
Taxation now is framed in conservative terms. Romney and Obama warred about whose tax plan would save the middle class the most money. But if we, as a nation, are actually concerned about our national debt, while still committed to our entitlement programs, shouldn't we shift the conversation onto progressive ground? Taxation is not an annoyance. It is a civic duty. If we go to war, we need to pay for it. If we want entitlements, we need to pay for them. As citizens of the most prosperous country in the world, we need to re-frame the conversation about taxes, and decide that there are some things worth paying for.