Miraculously enough, we bought a duplex in Vancouver back when housing prices were merely high (as opposed to their present level, which is absurd). But that doesn't mean we have a stake in keeping housing prices high; if anything, our interest lies in seeing the bubble burst, too.
But wait, you think: don't all us home owners have a stake in keeping prices high? Only if we're planning to get out of the market all together. Speaking personally, when we sell our house it will be so that we can buy another house in Vancouver, so it doesn't matter to us whether we're buying and selling for thousands or millions — we'll end up with the same size mortgage either way.
That's not to say that we're unaffected by the market bubble. On the contrary, high housing prices hurt home owners too. They push our friends into neighbourhoods that are far away, so we see friends less often. They encourage people to move out into the 'burbs, which means more cars on the road and more smog. They push talented people doing crucial comunity service jobs into jobs with higher incomes, so they can afford crazy mortgages.
But the most crucial way that high housing prices hurt home owners is by hurting non-home owners. When our community becomes too expensive for an ever-larger number of people to buy into and put down roots, it pushes many groups of people right out of the Lower Mainland and makes our community ever more homogeneous and boring. Do we really want to live in a community where you have to be a millionaire to have a home? No way.