for starters look here: [Quantifying the problem of immigrant imposters is a challenge; neither the IRS nor the Social Security Administration has tried]
"The secret list of ID theft victims" http://www.msnbc.msn.com/id/6814673/ Jan. 29, 2005
later...
It wasn't a problem for you. You said "The number of employers who have been prosecuted for illegal activity, e.g hiring non us citizens at slave wages, taking false social security numbers or avoiding IRS withholding is practically zero "
Then you give me this link on identity theft that has no employer arrest information at all. Why even respond?