Social Security

Tucson Citizen - Solving Social Security is no big deal: Privatize!

As an investor, I've always wondered why Social Security is such a problem.
What's so difficult about managing this particular Trust Fund, and why is it so different from other investment accounts that pay out a constant stream of income?
The private sector does it routinely with defined benefit pension plans and fixed annuities, so what's the big deal? Is Social Security failing because it hasn't been invested soundly, or is there some other reason?