Thanks for down-voting my last comment! Here's a better one - the loan is still based on trust and once you've given away your private key information you can never take it back. So you're left with either changing your key or having the giver of the loan have the keys to your account.

While this may not seem like a problem - there are times when even good people become desperate and do desperate things.

Are you going to trust someone with the keys to your account that was able to generate enough money to pay back the initial loan?

I wouldn't - but everybody has to decide these kinds of things for themselves.