Craig,
I don't know of a better place to put the money than Treas bonds. My only problem with that is the low rate of interest those special SS bonds pay. Because of that low rate, I think the fed govt is keeping it's debt expense low at the expense of the SS fund. I.e., using SS funds to 'back door' fund the general account (Of course, the SS money itself is a front door source of funding, but that's another matter.)
My fear in investing in equities on the stock market is what happens to SS when the stock market tanks, as it does periodically? It's bad enough peoples' IRA's and 401(k)'s tank, but SS too? This is my problem with ideas of privatizing SS.
Then there are many other problems, mostly involving opportunities for mischief. SS is a lot of money, wouldn't choosing a stock (or stocks, of course) to invest in drive it's price up higher? Of course it would. Who chooses the winners and losers?
Would the govt personnel in charge of investment decisions be influenced to choose investments based on political ideology? (Or worse, campaign donors)
Is investing in companies and regulating them at the same time incestuous? I think so. Could it lead to conflicts of interests?
We're now trying to clamp down on a type of insider trading. It's a 'new' kind, where regulatory decisions, or awarding govt contracts etc can influence share price. Throwing SS into this mix leads to all kinds of ethical questions. If a company gets awarded a big govt contract is it because it's the best, or because SS owns a bunch of it's stock? If it dumps a stock is it because the SS trustees know some expensive regulation are coming on the way that will reduce the price of shares?
Would the funds be used to bailout companies or countries without it being called a bailout?
I see too much potential for problems, real or perceived, for it to be advisable to invest in anything other US Treas.
Lastly, as an a finance professional, there is simply nothing safer than US Treas if you want to protect against principal loss. And I believe assuring no loss of principal should be the number 1 priority for a program like SS.
Fern