Collateral is a must, and most of the time the offered collateral is the forum account here in bitcointalk. That is why most of the users who can get loan is the higher rank and no newbie can get a loan.
That is why loan is very risky method to earn bitcoin, much better to give loan personally which you know the person who applying and you can chase them if they do not pay.
Most lenders do not accept forum accounts anymore because if the person defaults on the loan now they have to sell the account to recover their money and many do not like this activity since they are against it since account sales most of the time leads to scams.