I think in some sort of theoretical way, a stock market crash, should hurt DVC sales. Market Crash means low prices, which is the time one should be buying stocks. So if the market crashed as I was looking to buy a dvc contract, I would put the money in the market since it is down, as opposed to buying the dvc contract. That being said, I do not think most people think that way, if they have the money and want to buy, they will.
It is, as mentioned before, unemployment and low wages that would hurt sales.