Should there be a public option for the credit market?

[Redalgo]

I've been eying this thread with curiosity since it was started because for a few years now the idea of having a single, national card for personal credit and debit has been attractive to me. I wonder about the borrowing of businesses in a similar respect too but am reluctant to lay out an argument one way or another, seeing as I've never heard anyone authoritative discuss the pros and cons of such a course of action.