If anything should happen to the government retirement program, an awful lot of folks are going to be stuck. As you can see from the chart, Social Security payments constitute by far the most important source of retirement income for more than half of elderly Americans. Only at the highest income level do earnings and income from assets represent a bigger share of the retirement pie. Princeton economics professor Uwe Reinhardt sums up the situation at Economix:
I see a people with a very short horizon over which they appear to measure their cherished "independence from government" -- the years when they are younger and healthy and have a good job, ideally one that provides them with good health insurance. As they grow older and sicker, however, very large cohorts of Americans have come and in the future will come to look to the rest of society -- that is, government -- for their main source of income maintenance and health care financing, even as they may protest, at political rallies, that they want "government out of their Medicare." For millions of retired Americans, the bill for only one serious hospital episode would wipe out whatever lifetime accumulated net worth they have.