This is a topic I have considered.
My US based assets are primarily with Vanguard (90%). No organization is fraud proof, but Vanguard is about as close as you will get in the US.
I have dealt with institutional risk at the currency/government level, which, based on my years as an international mining professional, are more relavent to preserve assets from the erosion of fraud, inflation (a form of currency fraud, really) and the more frequent losses due to tax and political risk. You can use Vanguard as a basket to hold US investments without any real basis for concern. For foreign investments, such as foriegn funds, you could consider holding direct ETF's in country funds, which can also be held in vanguard, or Schwab, Scottrade, or any discounter. If you want to go full bore to insulate yourself from US political risk, check out UBS, Barclays, or one of the similar international "brand" names for an out of US account and have a world wide access card set up for international ATM access. This would not be something you should do without your own due dilligence, creates potential US tax review, as there are tax reports and related US side obligations that seem to presume you are forever a servant of the IRS, but it is a country risk hedge. Should the US as we know it fall you might want to have a plan "B" such as a home in Sri Lanka or some similar "safe haven" should catastrophic events unfold in the US and money to fund even if the US freezes assets or the system totally fails (currently unlikely).
The other option is a survivalist camp in the west. Having lived in mining camps in the middle of remote outposts most of my working life, I suggest Sri Lanka.