Comrades,
Scanning the relevant sections of the book Com. Wojtek kindly cited (The New Americans: Economic, Demographic, and Fiscal Effects of Immigration http://books.nap.edu/books/0309063566/html/index.html), I see a nice answer to the conservative claim that immigrants are fiscally ruinous. All this study really says is that if a lot of poor people move into your state, the chances are that they will cost the native taxpayers money. The back of the envelope agrees with this simple formula as stated. Yet this model implies a perfect, progressive cure for the problem - a well-enforced and high minimum wage. Rather than allowing businesses to enjoy the profits of paying low wages while shifting the burdens of impoverished worker to the taxpayer, force the businesses to increase value added per worker through better industrial processes. Since the main reason for hiring illiegal immigrants is that they can be paid illegally low wages, you undermine the entire illegal immigrant economy without having to resort to identity cards and the like.
peace,
boddi