Whatusay, you also have a good point, most nations are not as tolerant of this kind of behavior as we are in the US. Here, if arrested (which doesn't happen often), they simply are deported, or sometimes not even that, they are given a ticket for a court appearance, and usually just find their favorite document forger, and come back under a different name, and start all over again. (It happens, I used to work a job where about half the staff was illegals).
In Mexico, an illegal immigrant into their nation can face up to 3 years in prison, and in Mexico, the suffering someone would face in their prisons would equal about 20-30 years in an American prison. We are far more tolerant of illegals than the nation that send us the most illegal immigrants, isn't that ironic?