They may have not done anything wrong, but they are receiving three times in benefits to what they paid into the system. Medicare is unsustainable. What most people don't know is that the premiums paid into Medicare Parts B and D cover only 25% of the costs. By law, the General Fund picks up the rest, which is why Medicare will consume the entire federal budget if it is not reformed.
This graph shows that the average man and woman (average defined in the study as average income over their working lives and living to the average life expectancy) who start receiving benefits in 2010 get over 3 times more in benefits than they pay in to the system! Of importance, the study accounts for inflation by calculating all past taxes and future payments in 2010 dollars to provide an accurate comparison.
If the notion that Medicare recipients are simply "getting back what they paid in" is false then where is the money coming from? Simply, the excess received is being borrowed from younger generations and the cost is more than we can bear.