Actually, if they're on a formal payroll, they do have taxes taken out, IRS and SS; and many are, using fake SSN's (which a lot of 'legals' use also). If they are not on a formal payroll, but are getting paid in cash, most don't qualify to pay taxes, though many do using Individual Taxpayer Identification Numbers (ITIN) issued by the IRS which created ITIN's specifically for illegal immigrants. Those immigrants that do not report cash earnings join the millions of Americans who don't report cash earnings.

As far as the criminals, I'll bet you that number is a drop in the bucket compared to what we create here at home.

http://roygermano.wordpress.com/2011/02/28/do-illegal-immigrants-pay-taxes/
http://www.usatoday.com/money/perfi/taxes/2008-04-10-immigrantstaxes_N.htm

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>>I was living in Houston when the big influx of Vietnamese hit the Gulf Coast and generally the complaint was "they're taking jobs away from Ammuricuns!". I generally found that the jobs being 'taken away' from Americans were jobs that no American really wanted - or thought they were too good to take. Really, how many of the people bitching about the illegal immigrants really want to spend 10 hours a day, every day, picking produce and fruit? Or cleaning sewers? Or cleaning someone's house? That's what a massive majority of the 'illegals' do. I guarantee you they wouldn't, especially at the wages being paid.
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>And the illegals don't pay taxes (yeah - there have been a couple of examples of ones that do - out of millions). And the illegals clog up health care on the taxpayer's dime. And the illegals clog up other social systems on the taxpayers dime. And it's absolutely unfair to people who legally immigrated to this country to allow illegals to have a free unhindered ride.
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>And who knows who is coming in as part of the illegals? Criminals (yeah - lots). Terrorists? (no - they wouldn't be smart enough to do that now would they?).
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>Let's just open the borders and then bitch like the Europeans later.