Of course these incentives played a role in the current crisis! Excessively low interest rates which made it too easy for people to borrow too much (see John Taylor's new book: short, compelling and accessible), but the tax treatment intensifies bad incentives like a magnifying glass heating up a bug.

And while you are on the subject of behavior distorting tax incentives, why do we insist on making employer paid health benefits tax deductible but employee purchased benefits taxable? It's grossly unfair to the un-insured worker who has to cover himself and it creates a terrible incentive to business to offer gold-plated plans which only serve to further inflate the cost of care in this country.