Social Security and the great "Trust Fund" myth

I was reading through this month's Atlantic magazine and came across a letter from one Nelson Dahl of Seattle, who insists that the a recent article by Megan McArdle spread "misinformation" about the Social Security program and that the SS Trust Fund has "nothing" to do with the federal budget. In response, McArdle doesn't equivocate:

The Social Security surplus has everything to do with the federal budget. Social Security’s "trust fund" consists of special Treasury bonds; when the Social Security Administration is no longer collecting as much in payroll taxes, it will start using up those bonds to cover expenses. In order to make the payments on those bonds, the federal government will have to raise taxes, cut other spending, or borrow money in the private markets - which is exactly what the government would have to do if there were no trust fund. Social Security collected less in taxes than it paid in benefits for the first time this year, and starting late in this decade, it will be permanently in deficit. That means the federal government is going to have to find ever-increasing sums of money that it can transfer into the Social Security system.

The Social Security Trust Fund has always been an enormous accounting trick where the government loans money to itself. For decades it has covered up the true size of the federal deficit but now the situation is about to be turned one-hundred-eighty degrees.