to be fair, social security as marketed and social security as enacted and in reality are two very different things.
there is no "investment" of "your" money. it's a paygo program. current workers fund current retirees. the only problem in the future is that americans aren't having as many kids as necessary to support their longer lifespans.
more immigration could solve the problem, as could a change in childbearing statistics in the right direction.
as payers into the system, we are really no more "entitled" to a benefit 20 or 30 years from now than any other recipient of a government expenditure is entitled to a payment until it arrives in their bank account.
the reality is that the government has been treating social security taxes as general revenue taxes for over 25 years. the trust fund is pretty much a myth. the fiscal pain starts as soon as those taxes are no longer available for general expenditures. i believe that happens sometime around 2015 or so. i do think something will get worked out to "save" SS. some combination of lower benefits, higher retirement ages, more taxes on benefits for those who have saved, even lower benefits for those who paid in the most (i.e. reducing the difference in payouts between low earners and high earners), etc. it's tough for anyone below around 50 to have any idea what to expect. so we might as well plan as if we'll get nothing and hope for better.
the one fact that you have wrong is the efficiency of social security (although you did say "allocating money efficiently" so perhaps you weren't attacking the efficiency of the program itself). it is an eerily efficient program. its costs are significantly lower than any remotely similar private sector program. (economies of scale help the government on simple pay-in, pay-out programs).