IS a risky method,some members can use as collateral hacked account.Is a good idea if you only lend money to trust members with a high rank and trust.
it is not risky if you know how to spot these things. for example you can find out if the password was recently changed here in forum security log:
https://bitcointalk.org/seclog.phpalso you should always ask for a signed message from and old bitcoin address.
the most important are be careful on approving loan ,
you can always looking for reference on people who want the loan like how good their reputation ,
how old they are being active in this forum etc , you can learn all of it once you have an experience ,
so better you start a low amount loan and get your experience.