Earlier quoted context omitted.
Also mortgages.
Are mortgages really debt though? Because even though you owe, you also own as much as you owe (except during a market downturn of course). Whereas debt for a depreciating asset (like a car, or most things that go on a credit card) are what I would consider "real" debt. In other words, keep your net debt low or non existent (when looking at a balance sheet).
Never forget though, you are paying quite a bit for the use of that money (i.e. the banks). This is mitigated in a rising market, but lots of houses (well land, really) don't appreciate fast enough to counter this.
Not to mention the additional costs. It might be more accurate to think of your house as a depreciating asset (the house) bundled with a (hopefully) appreciated asset (the land it is on)