If Social Security were a private company it would be considered a pyramid scheme and shut down. Imagine someone published a Fidelity internal memo to Wikileaks stating that all shareholders under age 40 were required to keep investing 12.5% of their salary every month, could not sell, and would receive a negative return upon reaching retirement age. It's so fafetched it's laughable.
I don't have a problem with the government requiring a 12.5% retirement fund outlay from workers. It's paternalistic but probably pragmatic. I do think it should be an investment based program rather than a pyramid scheme, and I do think workers should be guaranteed at least the rate of return of a very conservative market investment (such as a precious metal or a certificate of deposit would yield).
The original genius behind Social Security was that it was not a welfare program, it was sold as an investment program. However the books were cooked from day 1 because it achieved that only due to very skewed demographics (far more young workers than old workers/retirees), just as Madoff's fund was able to pay out returns only on the basis of having far more new investors than investors expecting returns.
So I'm opposed to the regressive nature of the Social Security tax mainly because the program is broken and thus it's only a regressive tax and not an investment program. Obama ran on a campaign promise of turning social security into a welfare program which simply means preventing the program from going bankrupt by deciding that only those who are deemed poor get the funds promised them.
Imagine if Madoff had tried to avoid jail by saying that he'd refund the money of all the poor people who invested with him. That's equally laughable.
Sadly, turning it into a welfare program is probably the most pragmatic approach, but if we're going to do that we should immediately do away with the payroll tax and allow the scheme to end so that those who don't aspire to be poor can start investing their 12.5% into an actual IRA. It would be fine with me if income tax rates had to rise a bit to cover the cost of Soc Sec as welfare.