Earlier quoted context omitted.
True, but what is more risky? Having most of your money in a single, non-liquid asset with a very local market or having most of your money in a diversified, liquid asset? I'm not saying owning a home is a bad idea, just having 80%+ of your money in it.
Diversification can include real estate. Besides, it's the leverage. You can buy $625,500 of house with 2.5% down + a monthly payment with a ~4% vig. Nowhere else can you get that kind of money at that kind of rate with ~$16k down. Then if you're smart you invest other money other places to diversify. You can live in house, unlike Vanguard funds. But you should have both.
Here is my nightmare scenario: I live in the Bay area and if I wanted to buy a single-family house, I'd be looking at $900K at a minimum (if you avoid the really run-down/dangerous areas of the city).
Let's say I have the down payment of 20%. That's $180K. I buy the house and I can swing the $6000 per month in PMI, utilities, maintenance, etc.
Then the market takes a dip of 20%. If you own a $200K home, the hit would be $40K. That would suck, but with a good paying job, you could handle it.
In SF, a 20% drop (still within the realm of possibility) means you just lost $200K (if you include the other costs of closing on the home). $200K would be 5+ years of savings down the tubes.