I just thought about this today. Every time you are transacting with bitcoin, you will be told that you have to wait for bitcoin confirmation. This is common with bitcoin gambling sites. What I know is that bitcoin transactions are irreversible. Then why is it that you have to wait for the confirmation before initiating anything?
Maybe because if you use a low fee, you can revert your transaction.
Also if you don't depend of any confirmation, the blockchain will be useless, the "3" confirmations is something to avoid scammers.