Last week, Amazon decided to expand the B&M presence of its famed e-reader by throwing Best Buy the same bone already thrown to Staples and Target, and it looks as if "this fall" is about to get going. We've received word that demo units are already popping up in Best Buy locations (for training and education purposes, we're surmising), and mere mortals should be able to procure them starting next week. We suspect the $139 Wi-Fi and $189 3G model will both