Usually collateral is supposed to be equal or more than the amount borrowed, especially in a situation like this where there is no 'credit score' to use to determine likelihood of default.
Dharma Protocol doesn't require that the value of collateral be greater than the principal of the loan, but we do expect the market will demand full- or over-collateralization.
I asked that assuming people put up 1 eth as collateral to borrow 2 eth.