The creator doesn't need a backdoor; the early adopters have gigantic stacks of BTC that has never been used. The appropriate concern is not that they have a backdoor but that they flood the market and make it crash.
The exchange or Bitcoin itself? The code is open source and actively developed. Many people come over to bitcointalk asking about certain sections of the code. Many many eyes are looking at the main client source. Its highly unlikely there is a backdoor that has been missed.
I almost bought $500 worth of BTC back when they were trading for pennies. Now, who knows if they would have survived two hacks, or if I would have had the patience to hold on to them, but I sometimes wish I'd pulled the trigger.
