After doing a search, I found that most reports were coming from local news organizations from across the country. They tended to be tailored to local interest and there were few, if any explanations. There were the usual suspects; elderly drivers, intoxicated operators, and distracted drivers. There was one explanation that was simply that the brake and accelerator were closer together and smaller and that resulted in "accidental acceleration". So, I searched for hard data and have so far found only a small pool of information.
The Insurance Institute for Highway Safety has information on fatalities caused by running into buildings, but no other hard data. The most recent from 2009 reported 53 fatal accidents involving buildings. Even the US DOT,(Department of Transportation) through NHTSA, (National Highway Traffic Safety Administration), does not record this type of accident. However, they did have an interesting survey on distracted drivers here. This, coupled with excessive speed, seems to be the most reasonable explanation for the increase in these types of accidents.
If any readers have similar observations or can either broaden or narrow the reasons, please comment. I certainly could have missed something important. Until then, please use the door...