I was just reading this article about Mutual Banking which seems to fit the use of bitcoins as money and how a bitcoin bank would conceivably work.
It was written in 1889 by William Greene http://www.the-portal.org/mutual_banking.htm
Once the Mutual Bank is operating, money will be available practically without interest to, any responsible producer, so that his independence will no longer depend upon the whim of the usurer, but upon his determination and his ability in his line of work.
Its a long read but well worth it
The existing organization of credit is the daughter of hard money, begotten upon it incestuously by that insufficiency of circulating medium which results from laws making specie the sole legal tender.The immediate consequences of confused credit are want of confidence, loss of time, commercial frauds, fruitless and repeated applications for payment, complicated with irregular and ruinous expanses. The ultimate consequences are compositions, bad debts, expensive accommodation-loans, law-suits, insolvency, bankruptcy, separation of classes, hostility, hunger, extravagance, distress, riots, civil war, and, finally, revolution. The natural consequences of mutual banking are, first of all, the creation of order, and the definitive establishment of due organization in the social body, and, ultimately, the cure of all the evils. which flow from the present incoherence and disruption in the relations of production and commerce. (The Radical Deficiency of the Existing Circulating Medium 1857).