Here is one rebuttal:

http://money.cnn.com/2011/04/28/news...dex.htm?hpt=T2

An intersting quote:

He argued that most of the company's profit comes from its overseas operations, and that earnings in its refining business, which converts crude into oil and diesel, make up only 6% of its earnings.

In response to recent criticism of tax loopholes for the oil industry, Cohen said Exxon has paid nearly $59 billion in U.S. taxes over the last five years, including $9.8 billion last year.