Sometimes, it pays to reread the work of the masters. Like Yale's Robert Schiller, the authority on home prices. A year ago, the Yale economics professor published a brief summary of his latest work on long-term housing values, called "Long-Term Perspectives on the Current Boom in Home Prices." No surprises: Housing pretty much matches inflation -- exactly what you'd expect from an asset that, for the vast majority of people, doesn't produce anything of economic value.

I know that flies in the face of what the home-fetishist sales staff at the National Association of Realtors says, but the problem with Shiller (and by "problem" I mean "virtue") is that he uses long-term data to prove his point. Oh, and as far as I know, he's not on the payroll of the six-percenters, and doesn't depend on the home-industry bigwigs to keep the lights on. Unlike those folks up at Harvard, who are beholden to Centex (NYSE:CTX), Freddie Mac (NYSE:FRE), Fannie Mae (NYSE:FNM), UBS (NYSE:UBS), Home Depot (NYSE:HD), Sherwin Williams (NYSE:SHW), and others, Shiller is freer to call it like he sees it. And he saw a major bubble.

We're already seeing it deflate, and we're seeing many of the real estate apologists rush in to reassure us that the bottom is here, or near. They make the tired arguments about "strong economic fundamentals" and "wage growth." (Pop quiz: How many of you have seen your wages increasing at a 20%-per-year clip or better?) But none of them touch upon what I find to be Shiller's most interesting point.

It's the fad, stupid!

Until the past few months, real estate swapping was an enormously fashionable thing to do. The evidence has been right there in front of our faces: the ads on pop radio for zero-down, no-doc ARMs. How many flipping and home makeover shows do you have to surf through before you can find something decent to watch on TV? By many accounts, upwards of 40% of recent buying was second-home or "investment."

We've seen plenty of attempts to quantify the upcoming supply that will be owed to tightening credit standards, as well as foreclosures and hypothetical interest-rate hikes. But that leaves out a very interesting piece of the puzzle: What will happen to supply and demand now that flipping real estate is becoming as fashionable as Madonna, pet rocks, or parachute pants? That's the question none of those bubble apologists seem to be able to answer.

Can you blame them?

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At the time of publication, Seth Jayson had shares of Home Depot, but no positions in any other company mentioned here. See his latest blog commentary here. View his stock holdings and Fool profile here. Fool rules are here.