Well I haven't read the full article; from my standpoint it seems to wander in and out of causal arguments. At the crux of this issue is the average american's ability to pay thier debts. When interest rates were low and the housing market was booming, a lot of people took advantage of these "subprime"
variable mortgages and took on quite a large debt load becasue the lower interests made the payments manageable.
However having a variable mortgage means that when interest rates go up, so do your payments (to reflect the new ammortized interest rate). With each increase in interest rates you get a certain number of people (who maxed their
Total Debt Service Ratio (aka TDS)) are not able to keep up with the payments. Without debt restructuing this can quickly turn into a loan default situation and the mortgage companies that made the deals quickly loose out on the cash flow that mortgage generates. Even with the sale of the asset (house), losses are incurred and nobody is happy with the situation.
Putting this on a national scale the losses are scary (kind of makes you think then about the profits these companies are pulling in eh?) and the market gets all jittery about other related bottom lines. However the amount of market panic makes me re-evaluate the assumption of rational market behavior, as concerns over the average american TDS were discussed at least 4 years ago. It didn't seem to matter then because companies continued to approve mortgages to people who were likely to run into a loan default situation.
Really the lenders are partially to blame for being so agressive and ignoring certain risk factors, but the home owner should share part of the blame for over-extending their debt and not fully understanding the impact of likely interest rate hikes.
<edit> I should note that the linked article talks an awful lot about the value of the asset... that really only comes into play if the home owner decides to get out before a default in the loan occurs. The defaults arrising from being unable to handle the increases in payments has a much higher impact on the current situation as the housing market hasn't really burst
yet</edit>