"Paying something off for 30 years at 6% (tax-deductable) seems (on the surface at least) better than 30 years at 18% (non-tax-deductable)."
Well, that's why it should be a last resort versus not a consideration. If you're in so deep, there's no way out, ok. But, ideally, you'd cut back, budget, and pay the card faster than the 30 year time frame.
That tax write off comes at a cost. The additional debt changes your exposure on your primary residence. If something happens to your income, you have the additonal $XXk tacked on to your mortgage, and the corresponding payments. You can default on a card and keep your house. Default on your mortgage, and you're on the street.
This was a situation BEFORE bankruptcy reform, when it was easier to discharge the unsecured debts. But now (with some limited exceptions) this advantage got severely reduced or disappeared altogether.
So, now it is advantageous and prudent to shift the debt to equity. This is the key mistake credit card companies made lobbying for the reform. No doubt they will try to keep debtors in servitude by lobbying for the ADDITIONAL laws, prohibiting using equity to pay debt to them. Usurers do not want the debt to be paid, they want the interest ONLY!
Right, thats why I dislike automatic payments to my CC's. They wouldnt care if we were homeless as long as they are paid. If push came to shove I would default on them.