A better alternative to Social Security for those younger than 40 is the Chilean model. In Chile, you have the option of government run SS or you can opt to set up your own account in your own name which the government can not spend from, and you have choices of investments supervised by experienced investors.
I think I read somewhere else that the Chilean model has been changed. Better Google it for the update. It seems that the current fear of the government is that by having a voluntary aspect, a lot of lower income young people are not going to pay into the system, and will end up in trouble when it is their time to retire. Sounds a little like the Obamacare dilema. Unless insurance is mandatory, not enough people will get it to pay for the system. At least that is the impression I got reading about the new Chilean system.