What conclusion from this story can make everyone? - Never trust to the third party (YOU DO NOT NEED TO DO THIS!!!), use MultiSig transactions escrow for valuable things, only this can protect You from third party error...
If you had checked this thread. you would have seen MultiSig could not have prevented this. It was a simple, and costly, oversight from redsn0w.
You are wrong, I had checked this thread carefully. In case of using MultiSig (example):
1. Moreia want to loan 0.8 btc from lihuajkl and will provide own acc. for collateral.
2. redsn0w creates 2-of-2(3) MultiSig address from Moreia and lihuajkl public keys.
3. lihuajkl sends 1.6 btc to MultiSig address.
4. Moreia transfers his acc. to lihuajkl after tx completion.
5. redsn0w prepares 0.8 btc tx from MultiSig address to Moreia.
6. lihuajkl and Moreia check and sign it, 0.8 btc goes to Moreia.
lihuajkl is responsible for security of Moreia acc., in case of failure he can lose 0.8+0.8 btc.
Moreia is interested to return 0.8 btc, otherwise he can lose his acc.
redsn0w is interested to be everything smoothly because he can lose his 1% fee and reputation (funds can be returned back via private keys input).
7. Moreia returns 0.8 btc back to the MultiSig address.
8. After tx completion lihuajkl returns acc. back to Moreia.
9. redsn0w prepares 1.6 btc tx back to lihuajkl (-1% to redsn0w).
10. lihuajkl and Moreia check and sign tx, 1.6 btc goes back to lihuajkl (-1% to redsn0w).
Everything is secure. Everyone is happy in any possible situation.