How many times have you read financial-advice stories lecturing you to max-out on your IRA, save as much as you can in your 401(k), and even pay taxes now to change your regular IRA into a Roth IRA that will be tax-free until you die? Well, be careful how much you save. That's the message in President Obama's budget for fiscal 2014, which for the first time proposes to cap the amount Americans can save in these tax-sheltered investment vehicles. The White House explanation is that some people have accumulated "substantially more than is needed to fund reasonable levels of...