I still see a place where the model would need to put their tax ID on that form.
http://www.irs.gov/pub/irs-pdf/fss8.pdf
I have a lot of friends who are here illegal (just about all of them got here legal but have overstayed their visa) and you can't hire them because they don't have a social security number.
I'm not a lawyer, CPA, accountant, or any kind of legal advice person but I do know that my CPA says that I need a tax ID number for all payments I make to a private person.
This has nothing to do with model releases, 2257, or anything at all to do with IDs other then my CPA says I need a tax ID of I pay someone for any kind of work or service.
I guess since I'm not actually required to report anything under $600 per year the IRS wouldn't know if I had obtained the tax ID number but then if I was audited or checked to see if I was hiring illegal immigrants then I would be required to show that I had them fill out the proper IRS form.