These incidents happen all the time, and it almost always turns out that the driver was standing on the accelerator instead of the brake. (Naturally they adamantly deny it - if they'd thought they were pressing the accelerator they would have stopped, after all. Everyone underestimates how much your brain can play tricks on you in this situation.) Of course that does not eliminate design flaws as a cause - for example in the Audi case the pedals were too close together.
Ever since this all blew up I've suspected that it's quite possible the floor mat recall may have simply brought a lot of cases out of the woodwork that are actually not inconsistent with the normal "background" level of such accidents.