tl;dr: In an sense, all retirees are
parasites, whether they have large cash reserves or rely on a system like Social Security. Retirement itself is what is a
Ponzi scheme that takes what workers produce and gives it to
The right-wing seems to have declared a War on Social Security to go along with the more general War on the Welfare State and the War on Women. Their propaganda tries to get people to focus on the idea of ownership of a
personal account as the ideal so that they'll demand an end to the pay-as-you-go system that Social Security uses.
Their shell game with personal accounts relies on faith to a greater extent than does the fiat money that they like to condemn as having nothing at its base. Even if an economy uses hard, imperishable commodities like gold for its money, that money is not what the people in that economy ultimately want. What people want is those things, services, experiences, and so on that they spend their money on. Even in an economy with no credit, no paper money, and no base-metal coins but only with gold as the medium of exchange, if there are no things, services, experiences, and so on that people want, the gold will have no real value to them. To claim that gold or personal accounts will provide for people in their retirement is to require them to have faith that the economy will be productive enough when they retire and that their accounts will be flush enough then. A system like Social Security, on the other hand, only requires that the economy be productive enough.
In any economy, whether retired people have personal accounts filled with 1s and 0s on hard drives at banks or have personal stashes of gold under their mattresses or rely on an authority to move currency from people still employed within the productive economy to them, it is the total output of the productive economy that is relevant. Again, remember that it is goods, services, experiences, and so on—not 1s, 0s, or gold—that people want. Retirees are, by definition, unproductive and must take from the productive sector. That they give the productive sector some of their 1s, 0s, fiat paper, or gold does not negate the fact that they take output from production without having themselves produced anything during the relevant time period!
Assuming that the productive economy produces enough to meet everyone's needs, there is no reason that anyone in the society should have unmet needs. Relying on the market + personal accounts, though, virtually guarantees that some portion of the society will. If labor is heavily exploited and poorly paid, then laborers will not be able to buy what they produce, and only those with fat accounts will. If inflation erodes the value of accounts or if too many have been unable to save (see the previous scenario after several decades), then most retirees will not have enough even though the economy produces enough for everyone (see the 1920s).
The solution is for society to actively distribute wealth (that is, goods, services, experiences, and so on) by the proxy of taxing those in the productive economy and transfering the revenues from that tax to retirees. That is what Social Security does. All the talk of
Social Security accounts was necessary to sell the idea to people in the 1930s who were too proud to accept
welfare, but all that Social Security is is a formal system for transferring wealth from the productive to the nonproductive. However, private accounts are also just a system for transferring wealth from the productive to the nonproductive but with the element of high-stakes risk thrown in. Both systems for retirement are, thus,
Ponzi schemes, but Social Security results in justice instead of in a casino.