In computing history, there are many attacks against online transactions. There are failures and successes. Those who succeed made huge headlines and those failed are mostly hidden away or just fade off. Online transactions have always been very vulnerable because you have no way of knowing who you might be doing a transaction with. What if someone managed to spoof off their identity ?
Whether it is human error or computing error causing transactions online to fail, online transactions are always dangerous because of many unknown danger factors like trying to confirm the identity of the person you are doing transactions with and how trustworthy the other entity is. Is the other entity secure too besides yourself ? Are you actually secured...
Recently, a loophole in SSL/TLS have been found since September 2009. Imagine how many attacks could have occured using the loophole up till now, nothing have been published to seal the loophole.
This is big and very serious. I have never trusted online transactions. They are flawed. Imagine you use a service provider as your middle man and 'he' betrays your trust... you are definitely 'finished'.
I personally still think that online transactions are a danger to highlyu confidential stuff. I do rather personally communicate and meet the person in person than do it over the Net.