I've long said that an undocumented alien "living in the shadows in the USA" may very well be the last free man in this country. He lives, works and goes about his life as he pleases, and the State has no idea who he is.
Coming out of "the shadows" is the equivalent of snapping on the handcuffs -- because now he has a name, "papers" of some kind, and a taxpayer ID number (which is the real reason why the U.S. government is hell-bent on amnesty; make no mistake about it). What exactly is the upside to this?
Well, in the most extreme cases, you could “hang up” up your old SSN, work under the new one, and if your relationship with the IRS ever turns sour, wish them luck in getting their pound of flesh.