I just had a severe front tire blow out on my 2000 focus (ripped the side panel off!). after getting towed to the station for a replacement they discovered severe wear on my rear passenger tire only. it was worn THROUGH the metal on the very inside edge only. this was a new tire with less than 8 months of road time. I had quickly checked my tires the day before and failed to detect it. judging by the tire alone, i would have assumed that it had been riding on a 45 degree negative camber - it was that extreme.
this is not the first time i've had to prematurely replace tires on this car due to excessive wear, but by far the worst instance.