Large cities such as Los Angeles have bustling document forging enterprises. I think it was Leslie Stahl on 60 Minutes who did a story on this a few years ago; within minutes she had a fake SS card, fake green card and fake CA drivers license, which were sufficient to use as proof of residency in order to get a job.
I live in NYC, and we do have a thriving forgery industry here.
When I was in college I had a fake ID that could fool cops (I'm not so naive to think that his big market was college kids, it probably was illegals, he's since been busted).
NYC hasn't had the crack down they should on forgeries. Hell, if somone really wanted to, they could get not only get fake green cards, and fake licenses, they could buy a stolen identity and get the real thing.
My guys are legit, I've know them now for a few years and they came via referral, I also know the people they had to consult to get visa's and most of them are looking to become citizens one day. (Since this is NYC, and based on my lawyers advice, I've been told its not wise to even encourage or discourage the idea of citizenship, which is why my employees look at me funny when they start talking about it and I give them a blank expression).