In the long-term, you can expect the tax advantages of ownership to be priced into the housing market. This is one of the reasons (rampant speculation is another) price/rent ratios are so absurdly high. Fair value, without the tax benefits, would be a ratio of 9-12, given the costs of ownership and the illiquid nature of an owner's position. With the tax breaks, the fair value's higher, but it still doesn't make sense to buy at a P/R ratio of 20+, especially since rents are also likely to drop across much of the country.

In New York, price/rent ratios are above 40. A $2500/month apartment will sell for over a million. It only makes sense to buy at such a P/R ratio if you expect rents to skyrocket in the near future, and Manhattan rents are already starting to turn back.