Well I thought the OP was stating something obvious until I saw people disagreeing.

Consider a scenario where someone from not even a year ago took on a BTC loan to buy a new computer valued at $800 USD. Each bitcoin was about 0.4 cents each then, so they would need to borrow 200000 BTC. At a conservative 2% interest rate to offset risk, that's 204000 BTC.

Fast-forward to today and the loan is due. Each BTC is ~$8.50 right now, so the borrower needs to get $1,734,000 of value in order to pay for an $800 computer from last year.

Do you think someone who didn't even have $800 of purchasing power a year ago would have $1.7 million now?  Granted, I don't think bitcoin will increase in value so exponentially in the long run as it has in the last year, but the point will still stand regardless if you are placing a naturally deflationary currency against an inflationary one. Maybe lending might make more sense if there is equilibrium, but as long at the BTC economy grows and each bitcoin needs to account for more value, then that isn't going to happen.

EDIT: (This was similarly demonstrated in post 8, but didn't seem to be argued against sufficiently. Then again, I hadn't read all the replies in this topic yet. I was just posting in my few minute break here.)