I attended a Tax Reporting Seminar last year in the material that I still have from that class it says;
After 2001 (beginning January 2002), the financial institution must get additional documentation such as a passport proving their foreign status if the financial institution has a US mailing address for the customer.
I attended the same seminar in 2000 and they stressed the importance of a foreign address. The instructions for completion of the W-8ben state that "The permanent residence address is the address in the country where you claim to be a resident for purposes of that country's income tax. If you are an individual who does not have a tax residence in any country, your permanent residence is where you normally reside."
Now, since we have to get some other form of id to prove their foreign status, we would at least have that information from the passport etc.
Lori T