Here's some statistics on taxes paid to the Federal Gov't:

Corporate taxes comprises about 11% of Fed Income
Individual taxes comprises about 60% of Fed Income
The rest is employment (next largest), estate, gift, and excise taxes.

http://www.irs.gov/pub/irs-soi/04db07co.xls

The tax breakdown by income bracket goes like this for 2003 data (data taken from other sites):

The top 1% of individual wage earners paid 34% of the Federal individual Income Tax.

The top 5% of individual wage earners paid 54% of the Federal individual Income Tax.

The top 25% of individual wage earners paid 84% of the Federal individual Income Tax.

The top 50% of individual wage earners paid 96.5% of the Federal individual Income Tax.

This means the bottom 50% of wage earners only pay 3.5% of the total individual income tax but receive an equal and/or greater share than those in the upper 50%.

So why not a tax cut for the ultra-rich. They are the ones paying the lionshare of the taxes anyways for fewer benefits.