I think it is a great idea. We have been considering using a line of credit to acts as a buffer allowing us to complete sales "instantly".
By having funds at the exchange when a seller deposits coins, we can sell the same number at the exchange and thus avoid currency risk during the 6 confirms. The main reason we haven't done this is it would make us very long BTC. The traditional lending forum is looking for rates aproaching 1% per day which is simply not viable for any serious enterprise. 3% per month may be useful for our needs.
My only fear (and it is more for you and your investors) is the hot wallet. Is instant 24/7 funding that important to risk a Bitcoinica type event. I see you also have a cold wallet. It is unlikely we will ever need hot wallet access.
A couple things from the business owner perspective.
Funding requests should be strongly secured and verifiable. Nothing less than PGP signature should be accepted. I can't imagine a worse nightmare than someone impersonating our company, getting funds, and then you seeking repayment from us.
Another security option for businesses would be a hardcoded disbursement address provided at the time the business requested the LoC. If that option is chosen funds can never be disbursed to any other address without a new contract. The hardcoded address would be included in the contract and pgp signed by both parties. This would make any sort of impersonation attack a moot point.
Lastly if you wish us to open our books I assume you will be comfortable signing an NDA.
We've talked about security quite frequently. It's our top priority (well... profits are my top priority, but that necessarily requires security), and the dev is familiar with infosec.
Accounts will only be allowed one whitelisted address. It can only be changed with a 48h wait after the request, and I'll be personally calling the phone number on the account's file as 2FA. All transactions beyond simply viewing account information will require a short code from the person logged in which will never be emailed, so even if an account-holder's email account is compromised and they've used the same password on another site where the login info was leaked, a malicious person should be unable even to request a loan to the account-owner's BTC address. A phone call will also be placed to the number originally registered with if the request is in a large amount.
I will note that I will be liable for malicious actions by unauthorized users, not the account-holders - but that liability's limited to not charging interest on a "fake" loan unless coins were sent to a BTC address other than the account-holder's. If a malicious person requests 100BTC to the account-holder's BTC address, the account-holder would be liable for that 100BTC. If a particularly nefarious person were able to compromise the db and change the BTC addresses (the hot wallet ofc wouldn't be hosted on the app server), then I would be liable for the principle of the loan since the account-holder didn't receive the coins. By keeping a relatively small amount of coins in the hot wallet, my maximum risk is pretty low, but will allow those auto-loans to occur without me needing to be online 24/7. Of course, if it is compromised, it's a pretty darn good warning (and cheap, relative to what others have needed to pay) to me that everything needs to come down while we investigate and resolve the problem.
A PGP key will be requested, but not required, upon registration. A valid phone number, however, will be required. As to companies opening up their books, an NDA would be accepted, but companies wishing to keep their BLoC unfrozen must publish their financials to the public, and those records can be no more than 6 months out of date. Businesses will be required to file monthly with me, and they can opt to keep that private or have it automatically published on the public side of BDK-BLoC to fulfill their public disclosure requirement. I'll pull that requirement if enough companies refuse based on it that I have significant idling funds, but that's never a problem, even now. The credit rating is broken down into 10 categories which will also give the public a bit of an idea of the financials of the company (how the credit rating is calculated will be published in the mock-up, and the exact meaning of the numbers will be published when BDK-BLoC launches).