http://trac.syr.edu/tracirs/latest/147/
"...According to new data from the Internal Revenue Service only 30 of the nation's thousands of millionaires were subject to a face-to-face IRS audit in 2005. The very small number selected for the traditional and sometimes intensive audits were drawn from 184,054 individual tax returns reporting a total positive income of $1 million or more..."

But if you're poor, look out. Terror of the IRS keeps H & R Block in business.

http://www.taxgirl.com/irs-insists-m...-support-kids/
"...
According to the Seattle Times, Rachel Porcaro did all of these things. A single mom, she took a job at Supercuts in Seattle, Washington to support her two boys [[ages 8 and 10). To save on housing, she lived with her parents, paying them a nominal rent. She went without a car.
You’d think she was doing all of the right things.
Except you’re not the IRS.
Porcaro was selected for audit last year. When she asked why she was chosen, the IRS explained that she was too poor..."