Canon just announced that the EOS 7D and 5D Mark II can have their mode-dials replaced for a $100 fee to feature a locking mechanism as seen originally on the Konica-Minolta Maxxum 7D. This prevents accidental movement of the dial which could cause shots to be missed. Pentax has also used that design on their K-7 and K-5 and Canon recently added it to the mid-range EOS 60D, putting the higher-end models in an awkward position.
While we have seen plenty of minor firmware upgrades to digital camera over the years, and even a few more complex ones from Sony, this has to be one of the first time a major manufacturer is offering a hardware upgrade and certainly the first to do so for usability reasons. There was one manufacturer which offered a memory buffer upgrade, if my memory serves correctly, but I can’t remember which.