I think khafra's point was that not-disclosing your Facebook info will become in the future, what not-allowing a credit check is now.
That is, today, only people who are big credit risks would try to avoid a credit check when applying for a loan -- because a credit check is an expected thing.
In the future, linking your facebook account will be an expected thing in applying for a loan. So banks will assume anyone not allowing it is likewise a credit risk and thus ineligible for a loan, except possibly at usurious rates.
To me it seems a lot more likely that not sharing Facebook info would result in slightly higher interest rates, not zero credit.
My thinking is that the Facebook info will not actually be more useful than things in a traditional credit score, so it will only be used in addition to those things. That leaves people with no payment history, but historically banks have been plenty willing to take a try it and see approach with those people.
That is, today, only people who are big credit risks would try to avoid a credit check when applying for a loan -- because a credit check is an expected thing.
In the future, linking your facebook account will be an expected thing in applying for a loan. So banks will assume anyone not allowing it is likewise a credit risk and thus ineligible for a loan, except possibly at usurious rates.