Actually it's very true.
There can be a lot of argument about fairness of rates, and who receives services, and all of the other social value judgements that our society has to make. There can be no argument though that folks in the top xx% of the U.S. income scale inject the large and disproportionate bulk of income tax revenue to the government. It's really not close.
NTU tables 1999-2003
Analysis of 1999 CBO numbers
2003 NYT graph on gov't tax recepits
The very bottom xx% of income earners are eligible to receive money BACK to supplement their income through the
Earned Income Tax Credit (a
refundable tax credit) which can "result in a net payment to the taxpayer beyond their own payments into the tax system".