From what I know from the bitcoin protocol if a transaction is confirmed one time it's confirmed forever.
This is not entirely true. If orphant block shows up transactions will be reverted. Im not sure what happens then: are transactions resubmited by clients or just stay orphant. This could break up the btc flow in script and that is what I'm affraid of.After reading up on it a bit I agree 2 is the absolute minimum.
Most website considers transaction final after 1 confirmation and even unconfirmed transaction for small amout!
