After checking out the Wall Street Journal opinion piece offered above, you might also want to read this recent news story from the very same Wall Street Journal.
Sorry I don't know how to active link but you can paste in the url...

http://online.wsj.com/article/SB120468366051012473.html

The gist of the article:

The nation's top 400 taxpayers reported a total of $85.6 billion of income on their federal income-tax returns for 2005 -- an average of $213.9 million apiece, according to Internal Revenue Service data obtained by The Wall Street Journal.

The group accounted for 1.15% of total income in 2005, up from 1.02% the prior year -- and more than twice as large as its 0.49% share a decade earlier. It's the highest percentage since the early 1990s, which is as far back as the IRS data go....