Yes, I think there will always be a certain level of default rate. But people wont be able to just sign up for accounts to ask for loans because there is a minimum reputation needed to ask for a loan, so even tho we dont know if this person intends to keep posting in Steemit we will know that everybody that asks for a loan has been a blogger and has earned some rewards and reputation, so they risk their possible future rewards (unlike other p2p lending platforms they have something to lose).
However, I agree that if this idea takes form and a GUI is implemented then a personal ID verification would be a must.
I would like to state that the idea is 100% Open Source, anyone can take it, improve it and make a business around it. I have always thought of myself to be a better thinker than a developer, so I just like to throw this concepts out there.
Speaking of which, I will give you a preview of the idea I have for token implementation (this does not mean I will do it, they are just my personal notes): https://www.evernote.com/shard/s673/sh/b15e7d18-847a-472e-950d-bbfc4e2c8f45/e33506918d38af86bfdbb408124ce680