Ah, the question everyone loves to debate. It's true that Social Security will soon start paying out more benefits than it receives in contributions, as the bulk of the baby-boom generation phases into retirement.
The government's official position is that there is enough money saved to pay benefits at the currently scheduled amounts until 2041. The Social Security Administration admits on its Web site that benefits will likely be reduced after that, barring changes that improve the financial strength of the system.
Some critics say that benefits could be at risk as early as 2016 or 2017, when Social Security cash flow turns negative. They claim that since the money paid in over the last few decades is part of the government's overall budget, it is available only on paper; other branches of the government have spent it and left IOUs. In order to pay benefits through 2041, the government would have to borrow.