I think there's probably no worse idea than having the government become the bank-of-last-resort.
With places like Washington Mutual who have "free checking" programs, there's no excuse for poor people to be without banking services. Sure, Citibank doesn't do it, but if you're poor, Citibank isn't the right provider for you anyway.
I've known lots of people with "poor"-level incomes who won't use a bank because they don't trust them. Why that is, I can't tell you. But they'll use a check-cashing service instead. Makes no sense to me, but there you have it.
/jordan