This is a big surprise... NOT!

Imagine people who live in poverty and high unemployment are willing to come and work. Who would have ever thought people would be willing to do that?

WASHINGTON - A survey of mostly undocumented Mexican immigrants found that a majority want to stay in the country permanently, but many more would be interested in signing up for temporary work permits even if it requires them to eventually return to Mexico.* Immigrant activists upset over Utah 'driver privilege' bill * More on border issues [azcentral.com | news]

The problem is that those who hire undocumented workers would have to deal with documented workers. This would make it harder to exploit their labor and cost the employers more than the current system of minimal enforcement costs.