So, Obama is sending 1200 troops to the border in an effort to stem illegal immigration. Additionally, no one, and I mean no one, has deported more people than the Obama Administration. Go ahead, look it up on Google, I'll wait. You done yet? Okay, good, because the point of this article isn't to praise Obama's immigration enforcement efforts, its to pan them completely (though, the deportation increase is probably the result of the enforcement efforts at the end of the Bush Administration which are now finally being litigated).
So, let's ask the key question - why do people hire illegal/undocumented immigrants? Simple, they hire undocumented immigrants because the immigrants will be willing to be paid less than other workers and because they won't complain about abuse (out of fear of deportation). But these factors don't change when you change the supply of illegal immigrants by enforcement - they exacerbate them. Immigrants become less and less willing to speak up for themselves if deportation becomes a very real threat. For instance, when I worked for the Fair Housing Council, a landlord had two fake immigration officials threaten her tenants, and these tenants almost dropped their complaint (and they would have, but for the fact that the immigration officials were so obviously fake).
Now, if the enforcement was equally applied to both employers and immigrants, this would be different. The monetary value of hiring an undocumented person would drop, and employers would think that hiring an undocumented person wasn't worth the risk. But that's never going to happen. For one, its easier to find undocumented immigrants than employers, and its easier to prosecute them. Employers have "rights" and "lawyers" which make prosecutions expensive and risky. So, the Feds go for the easy target.
And that's been the state of immigration in the country for the past twenty years. Every Administration since Reagan has beefed up immigration enforcement, and the situation has only gotten worse. So, instead of trying to prevent immigrants from coming, let's reduce the economic benefit of hiring undocumented immigrants - give them documentation, full rights under the law, and let them compete with Americans on an even playing field.