Fannie Mae -- the Federal National Mortgage Association -- was created in the 1930s to facilitate homeownership by buying mortgages from banks, freeing up cash that could be used to make new loans. Fannie and Freddie Mac, which does pretty much the same thing, now finance most of the home loans being made in America.

The case against Fannie and Freddie begins with their peculiar status: although they're private companies with stockholders and profits, they're "government-sponsored enterprises" established by federal law, which means that they receive special privileges.

The most important of these privileges is implicit: it's the belief of investors that if Fannie and Freddie are threatened with failure, the federal government will come to their rescue.

This implicit guarantee means that profits are privatized but losses are socialized. If Fannie and Freddie do well, their stockholders reap the benefits, but if things go badly, Washington picks up the tab. Heads they win, tails we lose.

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Fannie and Freddie had nothing to do with the explosion of high-risk lending a few years ago, an explosion that dwarfed the S.& L. fiasco. In fact, Fannie and Freddie, after growing rapidly in the 1990s, largely faded from the scene during the height of the housing bubble.

Partly that's because regulators, responding to accounting scandals at the companies, placed temporary restraints on both Fannie and Freddie that curtailed their lending just as housing prices were really taking off. Also, they didn't do any subprime lending, because they can't: the definition of a subprime loan is precisely a loan that doesn't meet the requirement, imposed by law, that Fannie and Freddie buy only mortgages issued to borrowers who made substantial down payments and carefully documented their income.