Totally agree with you about the businesses that hire illegals, but remember, alot of the hiring isn't done by big corporations but small time under the table jobs.
And you are not going after the clerks as the target really, just as you aren't going after the clerk at the mini mart who sells tobacco and alcohol to minors.
The people who get into big trouble are the shop owners for not complying with the law, just as the people in this case are the people who run the Money Transfer shop you walk into to send the money. They are in this to make a profit/for cash, and if they lose money from breaking the law then they won't keep looking the other way.