Actually I think that while you are working and paying into Social security there is a CAP on paying Social Security after you make so much in a year..........I think you should have to pay on all that you make in the course of the year. http://money.cnn.com/magazines/moneymag/money101/lesson18/index4.htm
There is a cap on the income subject to payroll tax because there is also a cap on benefits received. Promised future benefit rise with the amount of payroll taxes paid, but less than proportionally.
It wouldn’t solve the problem. One reason is that under current law, it would actually increase benefits for those above the cap. But, even if you change the law, it makes very little difference.
The SSA has evaluated this proposal, and the results are on their website. All it does is delay the inevitable for a few more years.