Loaning people your money is a good way to lose it all quickly and all for what? A tiny piece of interest? Most people will likely just take out loans to pay them back until they build up enough confidence to take a big chunk and run off with it.
not if you have a policy of "never lending someone big amount of bitcoin without a valid collateral". you can sell the collateral if they default, and limiting the loan with no collateral to 20% of their account's worth will reduce your risk.