This article asks that question at the end of the first paragraph.
http://www.sfgate.com/cgi-bin/article.cgi?friend=/c/a/2008/07/17/MN8Q11OT2M.DTL
The one thing that really caught me eye from the article was this:
To put that number in human terms, the debt has reached $455,000 per U.S. household.
