Jeez, why dont you all just get out your torches and pitchforks while you are at it?
Although it is not conclusive, there is such a thing as unconscious driving phenomenon -
http://www.susanblackmore.co.uk/Conferences/tucson 2006.htm . According to the article, it happens to "mostly to experienced drivers on familiar routes". I believe this is the case with wind30, as he describes it.
At the risk of getting condemned by overzealous members of the CS community as well, yes, it happens to me too, on familiar routes, especially when I am on the phone (handsfree set, of course) or having a serious conversation with my passenger.
Its normal. It happens.