First, thanks for being such a kind and thoughtful person/group
Unfortunately, the US and UK lack heavily in such kind and honest people, as seen with the recent payment problems and scammers.
You guys usually lend 5 BTC or ~50 dollars to random people at a time, that's a ton of money!
Therefore, instead of just using posts to determine trusts, I highly suggest
1. You look at other sources of references, including ebay, amazon, etc
2. Obtain their phone number, address, and email for people lacking references. Make sure this isn't fake before you send the coin.
3. Spend some time doing background checks on other bitcoin merchant sites / forums
4. Talk to the admins of underground sites such as silk road, and have them refuse business to people using your coins, as most likely they are drug addicts never intending to repay
I understand according to your religion, its not right to charge an obscure amount of interest, but is it right to charge interest just to cover loses?