Check the validity of a transaction without history

[johnyj]

In real life, some one send you some money through internet bank, you use that money without worry that same money is spent twice, there is a bank settlement system behind this. Actually we do know that banks can double spending by making fake transactions in the settlement system, this could be avoided by assign an inspector looking through all their transaction history, but more frequently by just checking balance of each account

I suppose in the BTC world same thing may apply: If there is a mechanism to check the balance of each address against block chain and green flag those addresses which passed the balance test, then everything sent from that address is safe, so you do not need to know what happened in the past, just need to know that transaction coming from a safe address

Or even, each address have a credit rating, the higher it is, the more trustful it is

[Vitalik Buterin]

You can always use a third party service to verify incoming transactions for you. AFAIK, this is how Electrum works already.