First, the Clinton administration did not synthesize a surplus out of the social security trust fund; they simply had the good fortune to take office during a period of historic productivity expansion.

Second of all, the "IOUs" you're talking about are government bonds. For your argument to hold, you have to assert that the government is going to default on its own bonds.

Governments default on their own bonds often enough. Cf. Argentina plus a whole slew of third-world countries.

I'll skip the theory and offer a single data point: the employees of the Social Security Administration do not, themselves, use or pay into SS. Neither do any other US Government employees. That is, the people who know the most about the system think it's so good that they don't want any part of it. It's almost like they know something some of us don't.

I would suggest that the general fund is a Ponzi scheme backed by selling IOU's. We are borrowing more money to pay the interest on money we already borrowed and adding more debt on top of that. Long term we need to start borrowing less than the interest on our debt - inflation. Which is not all that high a number vs GDP.