It could be for the very same reason that every person who cheats on their taxes is not subject to criminal prosecution.  Certain actions are carried out by one division of the organization and then others are referred to another division for consideration.  Maybe the division that decides on these cases is still reviewing it or maybe they decided to pass on criminal prosecution. 

I'm not a lawyer but I understand that the employer must know he was hiring illegal immigrants.  I earlier referenced a lawsuit against Tyson Foods.  It apparently was caught actually conspiring to smuggle illegal immigrants into the US to work for it.  I believe that a company is off the hook as long as a person shows up with reasonable documentation.  A company has no obligation to actually verify a word on the documents.

"Hiring practices in illegal-immigrant-saturated industries are a form of play-acting: Millions of illegal workers pretend to present valid documents, and thousands of employers pretend to believe them. The law imposes no obligation on the employer to verify that a worker is actually qualified to work, and as long as the proffered documents are not patently phony, the employer will nearly always be insulated from liability merely by having eyeballed them. To find an employer guilty of violating the ban on hiring illegal aliens, immigration authorities must prove that he knew he was getting fake papers - an almost insurmountable burden."

boycott these companies?  Wouldn't that be a lot more effective than their current tactics?

I have a deep and abiding hatred of sting operations, but it seems only fair that if the immigration people were really serious about nipping this problem in the bud they would set up stings of such employers and prosecute them just as we currently prosecute drug dealers and stolen property fences.  After a couple of well-publicized stings and prosecutions we'd see a miraculous increase in document authentication by employers. 

Meat packing is one industry where employers have gotten away with murder for years.  The starting hourly wage of meat packing employees has plummeted as company operations have expanded and their working conditions have deteriorated.  This could only have been made possible by a seemingly inexhaustable supply of illegal immigrants willing to take such jobs and enforcement which focuses solely on the illegal looking for a job rather than on the one willing to hire him. 

I see this (and all other raids on illegals only) as the same thing as going out and rounding up all the drug users, leaving the dealers and suppliers unmolested and unfettered to continue to ply their trade, making millions in the process and many "new" users.

What is the enforcement value of a junkie versus a dealer or supplier? Hasn't it taken us years to figure this out? Perhaps INS needs to go have a word with DEA....

And in this particular case, insuring higher profits by using these people and not having to pay a decent salary/benefits for the job.

It just doesn't make any sense to me, common or otherwise.