I see a service opportunity here. Someone can offer a Credit Rating service here for a % fee from the lender. Though it's risky considering the service provider is liable for a defaulted loan.
For non-collateral loans, no one knows who will repay or not so I do not think any user will try to open such a service as the service provider will be responsible for defaulting the loan. Many reputed members with high-quality posts and merit defaulted loans. So, it is always risky.
It is not your fault! Who could ever realize that a member would default a $100 loan. Next time do check their activities for a at least a year before agreeing to any loan request. If they are active every day then the chances of them defaulting would be less. This is not a fixed solution but it will give you reassurance. I hope this low life comes back and repays the amount he owns you.
You are right but if we try to check ins and outs then a lot of users will not be able to get non-collateral loans but of them few might be really needy borrowers. So, for a few stupid people, I do not want to punish innocent people.