Private firms should be able to pay whatever they want to their employees. What the US Government is proposing now is not just too late and impossible to implement lest they are run directly by the government, it is counter to the spirit of capitalism. Read this.
It is up to the Boards of Directors of Wall Street and other firms to ensure that what is done within the firms are fair and proper to the shareholders.
"Excessive" payments in the past that led to bonus-fixated executives to sell whatever toxic assets to whichever unsuspecting clients was not "clean and proper". They, as we know now, hurt shareholders' interest. Along the way such tactics violated various checks and balances by SEC or other regulatory agencies which these agencies had failed to implement.
It is just mind-boggling to see the government trying to work with Wall Street with the same wrecking crews responsible for excessive payment checks as well as selling toxics.
This proposal to restrict salaries on Wall Street which I doubt will come to pass sounds more like a PR tactic to placate the boiling resentment of taxpayers who see Wall Street obscene bonuses continue to rise while theirs are either cut or, for many, worse -- they are out of a job.