I found this site
842,000 acres are lost each year to major fires
The past 2 years have been higher, 2006 was really bad
National Interagency Fire Center
Forests used to burn out on a reg basis. Brush & built up wood burned off naturally. Man has prevented this natural burn off, so the "fuel" has added up over the years. They did change the way they manage forests - not sure when. In some areas they now do controlled burns, but even those can get out of hand