WASHINGTON -- A year after Congress passed a landmark law intended to tame the excesses that produced the financial crisis, some experts contend that a crucial vulnerability remains: The largest financial institutions are still so enormous that their failure could again bring the financial system to the brink of disaster.The passage of the Dodd-Frank law has sowed a perception of safety that has spawned a dangerous complacency, they add."The next crisis will happen sooner rather than later," said Anat Admati, a professor of finance and economics at the Stanford Graduate School of Business.