The stark admission – made by the bank's chairman at the end of a more than nine-hour marathon hearing before the US Senate – came in spite of his assertion that "I think people trust us" as he tried to fend off accusations that Goldman inflated the US housing bubble.
Senator Carl Levin told the veteran banker that he "wouldn't trust" Goldman as he repeatedly asked whether the bank would disclose its position "when they're buying something you solicit them to buy, and then you're taking a position against them?"
"I don't believe there is any obligation" to tell investors, Mr Blankfein responded. "I don't think we'd have to tell them, I don't think we'd even know ourselves."