Can someone explain to me how social security isn't one big Ponzi Scheme?

[Mark]

I pay social security taxes now which isn't invested but instead it's paid out directly to those who are retirement age. I'm told this is OK because the next generation will pay social security taxes which will go into my pocket. Didn't Bernie Madoff go to jail for this?
Why can't I opt out of social security all together?...I don't pay the tax but I'll never receive benefits. I can get a better return in the market and I don't want the government to try and manage my retirement.