I'm in the lower middle class in Canada. This means I'm in the 25% tax bracket.
Because of some expensive fertility treatment, my family is in debt. We are paying about $3000 a year in interest. $3000 x 25% = $750. This is not a big difference if debt interest is suddenly deemed tax deductible. But a lot of people won't do this math, and will use the tax deduction to rationalize more debt. A bad social policy I would say.
I don't feel sorry for credit card companies when a bankruptcy is declared. They took a risk pushing cards on people and raising the limits.